Systems and methods for plasma processing

Abstract

An apparatus for plasma processing includes an RF power source and a set of resonant structures coupled to the RF power source. The resonant structure includes a first region and a second region adjacent to the second region. The first region includes a first antenna and a first coupling circuit outside the coupling of the RF power source to the first region, the first coupling circuit configured to adjust the power distribution of the first region. The second region includes a second antenna.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Non-Provisional Patent Application No. 18 / 146,253, filed December 23, 2022, which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to semiconductor processing technology and, in particular embodiments, to systems and methods for plasma processing. [Background technology]

[0003] Plasma processing is widely used within the semiconductor industry in the manufacturing and fabrication of high density microcircuits.

[0004] In a plasma processing system, electromagnetic waves radiated into a plasma chamber generate an electromagnetic field within the chamber, which heats electrons within the chamber, igniting a plasma that treats substrates in processes such as etching, deposition, oxidation, sputtering, etc. Summary of the Invention [Problem to be solved by the invention]

[0005] Non-uniform electromagnetic fields within a plasma processing chamber can result in non-uniform processing of a substrate because different portions of the substrate are processed with plasma of varying densities. However, non-uniformities may exist within the plasma processing chamber itself. Therefore, devices and systems that can control the spatial distribution of electromagnetic fields are desirable. [Means for solving the problem]

[0006] According to one embodiment, an apparatus for plasma processing includes an RF power source and a set of resonant structures coupled to the RF power source. The resonant structures include a first region and a second region adjacent to the first region. The first region includes a first antenna and a first coupling circuit outside the coupling of the RF power source to the first region, the first coupling circuit configured to adjust the power distribution of the first region. The second region includes a second antenna.

[0007] According to one embodiment, an apparatus for plasma processing includes a resonant structure having a cylindrical or axisymmetric shape. The resonant structure includes a plurality of azimuthal regions. A first azimuthal region of the plurality of azimuthal regions includes a first antenna and a first impedance control circuit coupled to the first antenna, the first impedance control circuit configured to shift a resonance of one end of the first antenna. A second azimuthal region of the plurality of azimuthal regions includes a second antenna and a second impedance control circuit coupled to the second antenna.

[0008] According to one embodiment, a method for plasma processing includes loading a substrate into a plasma processing system, the plasma processing system comprising a multi-region resonant structure, the multi-region resonant structure comprising a first region and a second region adjacent to the first region; igniting a plasma by supplying a first amount of power to the first region and a second amount of power to the second region, the first amount having a greater areal density than the second amount; and performing a plasma process on the substrate, the plasma process including generating a plasma of uniform density.

[0009] 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 explanation of the drawings]

[0010] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions which should be read in conjunction with the accompanying drawings.

[0011] [Figure 1A] 1 is a diagram of a plasma processing system embodiment, according to some embodiments. [Figure 1B] 1 is a cross-sectional view of a resonant structure embodiment, according to some embodiments. [Figure 1C] FIG. 1C is a circuit diagram of the resonant structure embodiment of FIG. 1B, according to some embodiments. [Figure 1D] 1A-1C are circuit diagrams of various circuit embodiments for a resonant structure, according to some embodiments. [Figure 1E] 1A-1C are circuit diagrams of various circuit embodiments for a resonant structure, according to some embodiments. [Figure 1F] 1A-1C are circuit diagrams of various circuit embodiments for a resonant structure, according to some embodiments. [Figure 1G] 1A-1C are circuit diagrams of various circuit embodiments for a resonant structure, according to some embodiments. [Figure 2A] 1A and 1B are top and perspective views of a resonant structure embodiment, according to some embodiments. [Figure 2B] 1A and 1B are top and perspective views of a resonant structure embodiment, according to some embodiments. [Figure 3A] 1 is a cross-sectional view of a resonant structure embodiment, according to some embodiments. [Figure 3B] 1 is a cross-sectional view of a resonant structure embodiment, according to some embodiments. [Figure 3C] FIG. 3C is a circuit diagram of the resonant structure embodiment of FIGS. 3A and 3B, according to some embodiments. [Figure 3D] FIG. 3C is a circuit diagram of the resonant structure embodiment of FIGS. 3A and 3B, according to some embodiments. [Figure 3E] FIG. 3C is a circuit diagram of the resonant structure embodiment of FIGS. 3A and 3B, according to some embodiments. [Figure 4A] 1 is a cross-sectional view of a resonant structure embodiment, according to some embodiments. [Figure 4B] FIG. 4B is a circuit diagram of the resonant structure embodiment of FIG. 4A, according to some embodiments. [Figure 4C] FIG. 4B is a circuit diagram of the resonant structure embodiment of FIG. 4A, according to some embodiments. [Figure 4D] 1 is a graph of frequency shift in an antenna with an inductive loop, according to some embodiments. [Figure 5A] FIG. 2 is a diagram of a control scheme for a plasma processing system, according to some embodiments. [Figure 5B] FIG. 2 is a diagram of a control scheme for a plasma processing system, according to some embodiments. [Figure 6] 1 is a graph of plasma ignition at low pressure according to some embodiments. [Figure 7A] 1 is a plasma power pulse recipe according to some embodiments. [Figure 7B] 1 is a plasma power pulse recipe according to some embodiments. [Figure 7C] 1 is a plasma power pulse recipe according to some embodiments. [Figure 8A] FIG. 1 is a circuit diagram of a multi-zone plasma system, according to some embodiments. [Figure 8B] FIG. 1 is a circuit diagram of a multi-zone plasma system, according to some embodiments. [Figure 9] FIG. 1 is a circuit diagram of a multi-zone plasma system, according to some embodiments. [Figure 10A] FIG. 1 is a circuit diagram of a multi-zone plasma system, according to some embodiments. [Figure 10B] FIG. 1 is a circuit diagram of a multi-zone plasma system, according to some embodiments. [Figure 11] FIG. 1 is a process flow diagram of a method for plasma processing, according to some embodiments. [Figure 12] FIG. 1 is a process flow diagram of a method for plasma processing, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0012] Corresponding numerals and symbols in different drawings generally refer to corresponding parts unless otherwise specified. The drawings are drawn to clearly illustrate 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.

[0013] Making and using various embodiments is discussed in detail below. However, it should be recognized that the various embodiments described herein can be applied in a wide variety of specific situations. 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.

[0014] According to one or more embodiments of the present disclosure, the present application relates to a system and method for plasma processing using a multi-zone resonant structure. Each region of the multi-zone resonant structure can include a single antenna or multiple antennas dynamically configured to operate together in real time. Regions can be directly selected and controlled using radio frequency (RF) pulse modulation (e.g., modulating duty cycle, frequency, or power), electronic impedance control, or a combination thereof. Power can also be supplied as continuous wave RF with two or more frequencies supplied simultaneously (with sufficient frequency separation) to select and control different regions. Plasma density control can be achieved by fast control of power delivery to the regions, such as pulse-to-pulse power control and control of power within a pulse. Region control can enable plasma ignition at very low pressures and can be achieved with pulsed plasma. Feedback control of plasma density and low-pressure plasma ignition can be enabled using sensors (e.g., optical and voltage sensors) embedded in each region.

[0015] Instead of selecting and controlling regions by separately supplying power to each region with discrete pulse amplitudes and durations, multi-tone power supply combining two or more frequencies and amplitudes may be used to select and control the regions. Using multi-tone power may increase complexity. For example, power supply and measurement may require adjusting the frequency separation of the two regions to avoid being too close, which may result in excessive complexity limitations. Thus, the following embodiments are described using power separation by supplying discrete pulses to simplify control and measurement. However, those skilled in the art of RF modulation and measurement will understand that multi-tone or frequency modulation (e.g., as used in FM radio) is a viable method of power delivery and local uniformity control, and that embodiments including multi-tone or frequency modulation for local uniformity control are within the scope of the present disclosure.

[0016] Controlling the radial and azimuthal domains in real time can be advantageous for plasma processes used in semiconductor manufacturing, such as atomic layer etching (ALE). Plasma density uniformity can be altered by adjusting the coupling between antennas to account for the effects of chamber non-uniformities or non-uniformities across the wafer being processed. For example, chamber non-uniformities due to pumping ports or wafer non-uniformities can be compensated for during plasma etching or CVD processing by breaking the antenna symmetry with variable adjustment between the antennas. Uniformity control can be used to match radial and azimuthal etch critical dimensions or CVD film thickness patterns across multiple process chambers used to manufacture a given product. For example, different non-uniformities can be compensated for in different chambers so that each chamber in use generates plasma with the same distribution to achieve uniform results across the different chambers. This can be done in conjunction with dose adjustments across multiple wafers during lithography, enabling ultrafine uniformity control.

[0017] Metrology can measure incoming wafer non-uniformities and adjust plasma density uniformity on a wafer-to-wafer basis. Moving the location of maximum resonant current relative to the antenna (e.g., controlling current flow in the antenna arm) can be done by varying capacitive or inductive coupling to one side of the antenna arm. Capacitive coupling can be varied by using electronic switching between a capacitor and ground or by opening and closing a capacitor segment coupled to the antenna arm. Inductive coupling can be used to control power in the antenna arm using mutually coupled coils in each region to control the magnetic field.

[0018] Although aspects of the present invention are described primarily in connection with resonant structures in plasma processing systems, aspects of the present invention may be applicable to fields outside the semiconductor industry as well. Plasmas can be used to treat and modify surface properties through functionalization. For example, to prepare surfaces for paint deposition, plasmas can convert hydrophobic surfaces to hydrophilic surfaces. Furthermore, aspects of the present invention are not limited to plasmas. For example, RF can be used to thaw frozen foods or to dry textiles, food, wood, etc. In these various examples, and across multiple industries, controlling an oscillating magnetic field as disclosed herein would be advantageous.

[0019] Embodiments of the present disclosure are described with reference to the accompanying drawings. An embodiment of a plasma processing system having a resonant structure is described with reference to FIGS. 1A-1G. An embodiment of a multi-zone resonant structure is described with reference to FIGS. 2A-2B. An embodiment of a multi-zone resonant structure with capacitive circuit tuning is described with reference to FIGS. 3A-3E. An embodiment of a multi-zone resonant structure with inductive circuit tuning is described with reference to FIGS. 4A-4C. Experimental results of frequency shifting by an inductive loop are described with reference to FIG. 4D. An embodiment of a control scheme for a plasma processing system is described with reference to FIGS. 5A-5B. Experimental results of plasma ignition are described with reference to FIG. 6. An embodiment of a plasma power pulse recipe is described with reference to FIGS. 7A-7C. An embodiment of a multi-zone plasma system is described with reference to FIGS. 8A-10B. An embodiment of a method for plasma processing is described with reference to FIGS. 11 and 12.

[0020] Figure 1A shows a diagram of a plasma processing system embodiment 100. The plasma processing system 100 includes an RF source 102 (also referred to as an RF power supply), a multi-zone resonant structure 104, a plasma chamber 106, and an optional dielectric plate 114, which may or may not be arranged as shown in Figure 1A. Additionally, the plasma processing system 100 may include additional components not depicted in Figure 1A.

[0021] In an embodiment, the RF source 102 includes an RF power supply, which may include a generator circuit and a matching circuit (not shown). The matching circuit may also be referred to as a matching network. The RF source 102 may supply a single frequency or multiple frequencies. In an embodiment, the matching circuit couples the RF source 102 to the multi-zone resonant structure 104 across one or more capacitors, inductors, or both. In an embodiment, the matching circuit is distributed on the multi-zone resonant structure 104. The impedance of the multi-zone resonant structure 104 may differ from the impedance of the transmission line between the generator circuit and the multi-zone resonant structure 104. This impedance difference can lead to RF power reflections and reduced power efficiency. The matching circuit acts to ensure that the impedance seen by the generator circuit looking into the matching circuit is approximately equal to the internal impedance of the generator circuit. Therefore, the matching circuit improves the efficiency of power coupling from the RF source 102 to the multi-zone resonant structure 104.

[0022] In an embodiment, the RF source 102 is coupled to the multi-zone resonant structure 104 via a feed structure 103. In an embodiment, the feed structure 103 may include a transmission line, such as a coaxial cable, an interface with a conductive offset (see below and FIG. 1B), or the like, or a combination thereof. The RF source 102 supplies a forward RF wave to the multi-zone resonant structure 104. The multi-zone resonant structure 104 (also referred to as a multi-area resonant structure) includes one or more resonant structures, also referred to as a set of resonant structures (see below and FIG. 2A), and one or more radiating structures. In an embodiment, the one or more radiating structures are enclosed in a ground box, which blocks electric fields, reduces magnetic fields for human safety, and provides a ground return path from the plasma chamber 106 back to the RF source 102. The forward RF wave travels through the multi-zone resonant structure 104 and is transmitted (i.e., radiated) toward the plasma chamber 106.

[0023] 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.

[0024] In an embodiment, the multi-zone resonant 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 within the plasma chamber 106 from the external atmosphere. It should be appreciated that the multi-zone resonant structure 104 can be located directly adjacent to the plasma chamber 106, or the multi-zone resonant 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 multi-zone resonant structure 104 is at least partially embedded within the dielectric plate 114.

[0025] In one embodiment, the multi-zone resonant structure 104 couples RF power from the RF source 102 into the plasma chamber 106 to process the substrate 110. In particular, the multi-zone resonant structure 104 emits one or more electromagnetic waves in response to a forward RF wave transmitted from the RF source 102. The one or more emitted electromagnetic waves transmit from the atmosphere side (i.e., the multi-zone resonant structure 104 side) of the dielectric plate 114 into the plasma chamber 106. The one or more emitted electromagnetic waves generate one or more respective electromagnetic fields within the plasma chamber 106. The generated one or more electromagnetic fields ignite and sustain a plasma 112 by transferring energy to free electrons within the plasma chamber 106. The plasma 112 can be used, for example, to selectively etch or deposit material on the substrate 110.

[0026] 1A, the multi-zone resonant structure 104 is shown as being external to the plasma chamber 106. However, in various embodiments, the multi-zone resonant structure 104 can be located inside the plasma chamber 106.

[0027] In some embodiments, one or more operating frequencies of the multi-zone resonant structure 104 are in the range of 1 MHz to 6 GHz. In embodiments, the power provided by the multi-zone resonant structure 104 is in the range of 10 W to 10 kW and is determined by various factors such as the distance from the multi-zone resonant structure 104, the impedance value, etc.

[0028] 1B shows a cross-sectional view of an exemplary resonant structure (also called a cavity) according to some embodiments. The resonant structure may be coupled to ground through one or more capacitive structures (e.g., fixed or variable capacitors). It should be appreciated that the resonant structure in FIG. 1B is a non-limiting example illustrating possible configurations of radiating structures, capacitors, and ground planes without coupling to power, which may be coupled to power (e.g., an RF source) to generate a plasma.

[0029] In FIG. 1B, a radiating structure 210 (also called an antenna) is coupled to a ground plane 202 (also called a conductive plane) via two conductive plates 205. Exemplary resonant structures can have any suitable shape, such as a circular, polygonal, or ring-shaped structure in top view (see below and FIG. 2A). In some embodiments, the radiating structure 210 is a spiral antenna. However, the radiating structure 210 can be any structure suitable for generating a plasma. In some embodiments, the ground plane 202 is not grounded but is a common plate coupled to ground, for example, through a matching circuit.

[0030] Conductive plate 205 is coupled to radiating structure 210 by respective conductive offsets 208. Although conductive offsets 208 are shown as being coupled to opposite ends of radiating structure 210, conductive offsets 208 may be coupled to any suitable location on radiating structure 210. For example, one conductive offset 208 may be coupled to an outer edge of radiating structure 210 and another conductive offset 208 may be coupled to a center point of radiating structure 210. The cross section shown in FIG. 2A is taken through the illustrated conductive offsets 208. In embodiments, additional conductive offsets 208 or non-conductive (e.g., insulating) offsets are present between radiating structure 210 and conductive plate 205.

[0031] The conductive plate 205 is further coupled to the ground plane 202 via an insulating structure 204. The insulating structure 204 is comprised of an electrically insulating material, such as a dielectric material. In embodiments, the insulating structure 204 is comprised of air or a vacuum. In some embodiments, a mutual coupling coil 510 is attached to a sidewall of the plasma chamber 106 (e.g., a wall extending downward from the ground plane 202) to change the resonant frequency of the radiating structure 210 through mutual coupling.

[0032] FIG. 1C shows a circuit diagram of the exemplary resonant structure of FIG. 1B, also referred to as a floating resonant structure. Each capacitor 206 is formed by a conductive plate 205 coupled to the ground plane 202 across an insulating structure 204. The radiating structure 210 is coupled to the ground plane 202 through two capacitors 206, with the capacitors 206 located at opposite ends of the radiating structure 210 between the radiating structure 210 and the ground plane 202. The two capacitors 206 represent the equivalent capacitance of the conductive structure, including the respective conductive plates 205 and the ground plane 202. In some embodiments in which the radiating structure 210 is an inductor, the radiating structure 210 and the capacitors 206 form a CLC circuit. The mutual coupling coil 510 may have a variable inductance for adjusting the mutual coupling of the conductive offset 208 with the inductor 209. The conductive offset 208 may comprise, for example, a one-turn equivalent inductor 209 coupled to the mutual coupling coil 510.

[0033] 1D-1G show various circuit diagrams, for example, for the exemplary resonant structure of FIG. 1B, according to some embodiments. FIG. 1D shows a circuit diagram of a resonant structure having an antenna L1 (corresponding to radiating structure 210) coupled at one end to ground (e.g., ground plane 202) across a resistor R1 and a capacitor C1 (corresponding to capacitor 206) and at the opposite end to ground across a resistor R2 and a capacitor C2 (corresponding to capacitor 206). By adjusting the capacitances of capacitors C1 and C2 and the inductance of antenna L1, the resonant frequency of antenna L1 can be adjusted. In some embodiments, antenna L1 has an inductance in the range of 10 nanohenrys (nH) to 10,000 nH, e.g., 1650 nH; resistor R1 has a resistance in the range of 0.001 Ω to 0.2 Ω, e.g., 0.01 Ω; and capacitor C1 has a capacitance in the range of 10 picofarads (pF) to 10,000 pF, e.g., 900 pF. A node between resistor R1 and capacitor C1 is further coupled to a drive power supply via capacitor C3. In some embodiments, capacitor C2 has a capacitance in the range of 5 pF to 10,000 pF, e.g., 200 pF. With the above values ​​of the capacitances of capacitors C1 and C2 and the inductance of antenna L1, the resonant frequency of a single antenna (e.g., antenna L1) can be in the range of 400 kHz to 2 GHz. In some embodiments, capacitor C1 or C2 can be shorted to ground, and the circuit can operate as an LC circuit. Figure 1E shows a circuit diagram of a resonant structure similar to that of Figure 1D, but without the connection to drive power. Power coupling may be via an inductive drive circuit (not shown), an example of which is described in U.S. patent application Ser. No. 17 / 748,737, which is incorporated herein by reference in its entirety.

[0034] FIG. 1F shows a circuit diagram of a resonant structure similar to that of FIG. 1E, but excluding resistors R1 and R2. FIG. 1F is a general circuit diagram of a CLC circuit that allows for regulating the peak current from one end of antenna L1 near capacitor C1 to the other end of antenna L1 at its coupling with capacitor C2. While antenna L1 is shown as a single circuit device, those skilled in the art of RF antenna design will understand that antenna L1 is physically a long, elongated inductor (e.g., having a length ranging from 1 cm to 30 cm) that transfers power to the plasma in plasma chamber 106 (see above and FIG. 1A). The method of power transfer can be by inductive coupling (e.g., at higher currents) or capacitive coupling (e.g., at higher voltages). When operating in capacitive coupling mode, the high-voltage section of antenna L1 generates a high electromagnetic field on a dielectric surface (e.g., of dielectric plate 114), enabling plasma ignition at low pressures. The location of the high-voltage field can be controlled from one end of antenna L1 to the other by adjusting capacitors C1 and C2, for example. When operating in inductive coupling mode, the peak current along antenna L1 can be moved from end to end. This can also directly change the location of high plasma density regions in plasma chamber 106, such as near capacitor C1, near the center of antenna L1, or near capacitor C2. When pulsing the plasma and electronically controlling antenna L1, plasma density can be controlled region by region. High density regions can shift location within the pulse radially (e.g., from region 322 to region 312, see below and FIG. 2A) and azimuthally (e.g., between regions 312 at the same radial distance from center point 330, see below and FIG. 2A). The plasma coupling method can also change from capacitive to inductive coupling during a pulse of a few microseconds, or the plasma coupling can be balanced to maintain a combination of both coupling methods in one antenna-plasma power transfer area. In some embodiments, different coupling methods operate simultaneously in different physical regions (eg, regions 312 and 322, see below and FIG. 2A).

[0035] FIG. 1G shows a circuit diagram of a floating LC circuit that can be inductively driven and used as a basic circuit for inductive tuning (see below and FIG. 4A). For example, the floating LC circuit of FIG. 1G may be replicated an appropriate number of times (e.g., eight times) and used near an LC antenna circuit to inductively tune the LC antenna circuit. In some embodiments, inductor L1′ has an inductance in the range of 10 nH to 10,000 nH, e.g., 1650 nH, and capacitor C4 has a capacitance in the range of 5 pF to 10,000 pF, e.g., 1800 pF.

[0036] FIG. 2A illustrates a multi-zone and multi-region control area according to some embodiments, and FIG. 2B illustrates a multi-zone axisymmetric resonant structure 300 having an outer zone 310 surrounding an inner zone 320. The outer zone 310 and inner zone 320 may also be referred to as radial zones. FIG. 2A illustrates a top view of the multi-zone resonant structure 300. In some embodiments, the outer zone 310 and inner zone 320 have a cylindrical shape centered on a center point 330. The outer zone 310 and inner zone 320 may also be referred to as a resonant structure, a radial zone, or a cavity. While FIG. 2A is illustrated with two radial zones subdivided into regions having cylindrical shapes, it should be recognized that the shape of the regions (here, cylindrical) is non-limiting and other shapes are also contemplated. For example, plasma generation by an axisymmetric antenna may generate a cylindrical or circular plasma. As used in this disclosure, "axisymmetric" includes a structure (e.g., exemplary resonant structure 350, see below and FIG. 2B) that remains unchanged when rotated about an axis of symmetry (e.g., through center point 330) by an angle equal to 360 / n, where n is an integer greater than 1.

[0037] The outer zone 310 and the inner zone 320 may each include a respective radiating structure 210, a capacitor, and a conductive offset, as shown in FIG. 1B above. For example, the outer zone 310 and the inner zone 320 may each have a respective radiating structure 210 on their bottom side. However, any suitable internal structure may be used for the outer zone 310 and the inner zone 320.

[0038] The outer zone 310, the inner zone 320, or both, are divided into several regions defined by grouping segments or antennas. In the example shown in FIG. 2A, the outer zone 310 is divided into seven regions 312, and the inner zone 320 is divided into six regions 322. The regions 312 and 322 may also be referred to as azimuthal regions. However, the outer zone 310 and the inner zone 320 may each be divided into any suitable number of regions 312 and 322, such as 2 to 20 regions. The number of regions is merely an example for a given area, operating frequency, and amount of uniformity that needs to be controlled. For example, a large plasma processing system used in a display may have more than 100 antenna segments.

[0039] The regions can be directly selected and controlled using radio frequency (RF) pulse modulation (e.g., modulating duty cycle, frequency, or power), electronic impedance control, or a combination thereof. Tuning the regions to achieve asymmetric plasma density can be achieved by capacitive or inductive circuit coupling to the regions. This can be useful to enable plasma ignition at low pressures and to compensate for non-uniform chamber effects or non-uniformities in the wafer being processed. Sensors (e.g., voltage sensors or optical sensors) can be attached to each region and even to each antenna segment for region uniformity control. In other words, the sensors can be useful to maintain a specific amount of azimuthal or radial uniformity by varying the applied power between regions during tuning and ignition, and then over a longer period of time during the processing step. Examples of optical sensors include discrete photodiodes and optical emission spectroscopy (OES) systems. These may be coupled by light pipes or optical fibers to multiple optical measurement points, such as points above the plasma looking through the dielectric plate 114 from the top side of the plasma chamber 106, or points around the edge of the dielectric plate 114 to look through the side of the dielectric plate (see above and FIG. 1A). As an example, discrete photodiodes may be coupled by light pipes or optical fibers to measure along an antenna or at multiple radii around the perimeter of the plasma chamber 106. Optical sensors may also be arranged by configurable regions, such as region 312 in outer zone 310 or region 322 in inner zone 320.

[0040] FIG. 2B shows a perspective view of an exemplary resonant structure 350 having a radiating structure, also referred to as an antenna structure. In some embodiments, the radiating structure is a conductive planar closed ring structure with multiple antennas 362 (also referred to as spiral arms). The antennas 362 have n-fold symmetry about an axis passing through the center point 330. While FIG. 2B shows the number of antennas 362 as being eight, the number of spiral arms 362 is non-limiting and can be any number greater than one. The antennas 362 may form the radiating structure 210 (see above and FIGS. 1B-1C) and are coupled to the conductive plate 205 through conductive offsets 208. In some embodiments, one or more of the antennas 362 are electrically isolated from one another, such as by an air gap or dielectric material between the antennas 362 and the inner or outer ring of the radiating structure. Various examples of suitable radiating structures are described in U.S. Patent Application No. 17 / 649,823, which is incorporated herein by reference in its entirety.

[0041] In embodiments in which the antennas 362 are part of a unibody antenna (e.g., an axisymmetric unibody antenna), inductive circuits at the edges of the unibody antenna (see below and FIGS. 4A-4C) may couple with the magnetic field near the unibody antenna, thereby changing the current distribution in the antenna. In embodiments in which the antennas 362 are separated at at least one end, inductive circuits at the edges of the antennas 362 may act locally on each antenna 362, providing more discrete control of the current in each antenna 362. When antennas 362 are combined with a common capacitor (e.g., conductive plate 205 connecting two or more radiating structures 210, see above and FIG. 1B), the set of antennas 362 with the common capacitor form a control region that may use only one tuning mechanism, which may be inductive or capacitive.

[0042] In some embodiments, the conductive plates 205 are segmented and / or electrically isolated from one another. In other embodiments, the conductive plates 205 are continuous conductive plates or portions of a unibody conductive plate that form part of a unibody capacitor. In embodiments with a unibody capacitor, capacitive circuits at the edges of the unibody capacitor (see below and Figures 3A-3E) can vary the electric field distribution in the unibody capacitor. In embodiments with segmented conductive plates 205 that form segmented, isolated capacitors, the capacitive circuits can provide more discrete control of the electric field and current distribution in each capacitor and the associated antenna (which may be segmented or part of a unibody antenna). Capacitive circuits can be coupled to each segmented capacitor to allow for greater segment resonance variation between segmented zones, even in embodiments with a unibody antenna.

[0043] Capacitive or inductive coupling circuits can be used to adjust the resonant frequency or relative power output of the antenna in the radial and azimuthal zones, thereby achieving radial and azimuthal control of plasma density. FIGS. 3A-3E show examples of capacitive coupling circuits, and FIGS. 4A-4C show examples of inductive coupling circuits. The coupling circuits adjust the relative distribution of power to the antenna outside of the coupling of power from a power source (e.g., RF source 102, see above and FIG. 1A) to the antenna. The coupling circuits can be reactive or have resistive elements (e.g., low-resistivity metals that do not degrade over time). The choice of capacitive or inductive coupling to control the relative power to various zones can be based on the magnitude of control desired, mechanical access to the various zones, and magnetic coupling sensitivity across the entire power and frequency operating space. In some embodiments, hybrid coupling, including inductive coupling to one zone and capacitive coupling to another zone, can be used. This can achieve isolated control of each zone in the least sensitive manner while taking into account mechanical design constraints that may limit access to each zone by inductive or capacitive circuits.

[0044] 3A-3B show a multi-zone resonant structure 400 with capacitive circuit control of the zones. Capacitive circuit control can be achieved by using electronic switching of capacitors directly to ground, as shown in FIG. 3A, or by opening and closing capacitor segments coupled to an antenna, as shown in FIG. 3B.

[0045] FIG. 3A shows a cross-sectional view of a multi-zone resonant structure 400 featuring an external capacitive circuit, which is a detailed example of the multi-zone resonant structure 300 described above in connection with FIG. 2A. The example of FIG. 3A includes an outer zone (e.g., outer zone 310, see above and FIG. 2A) that includes an outer region (e.g., region 312, see above and FIG. 2A). The outer zone surrounds an inner region (e.g., region 322 of inner zone 320, see above and FIG. 2A) of an inner zone (e.g., region 322 of inner zone 320, see above and FIG. 2A) centered about axis 410. The multi-zone resonant structure 400 is shown without any feed or matching circuitry. However, it should be recognized that the multi-zone resonant structure 400 is a non-limiting example, and that embodiments may include any suitable combination of feeds or matching circuits, as described above and below. Further examples of suitable multi-zone resonant structures are described in US patent application Ser. No. 17 / 748,737, which is incorporated herein by reference in its entirety.

[0046] Capacitors 206A, 206B, 206C, and 206D are formed by coupling conductive plate 205 to ground plane 202 across insulating structure 204. While ground plane 202 is shown as being grounded, ground plane 202 may be floating or coupled to any suitable reference voltage. Each of capacitors 206A, 206B, 206C, and 206D may be grounded, floating, or coupled to any suitable reference voltage. Conductive plate 205 may be part of a unibody plate forming a larger unibody capacitor, or conductive plate 205 may be a separate segment of a larger conductive plate. In some embodiments, for example, in embodiments where some capacitors are grounded and other capacitors are floating, ground plane 202 has a gap or dielectric structure that electrically isolates the grounded capacitor from the floating capacitor. In the embodiment shown in FIG. 3A, a portion of insulating structure 204 extends to the top surface of ground plane 202 to provide an isolated electrical coupling between capacitor 206A and capacitor 402 used to adjust the capacitive coupling of the outer zone segments (see below).

[0047] 3A, the outer zone segment has outer capacitor 206A and inner capacitor 206B, and the inner zone segment has outer capacitor 206C and inner capacitor 206D. In other embodiments, the outer and inner zones may differ in the number or configuration of capacitors. For example, the outer and inner zones may have a shared capacitor and a shared conductive offset at their boundary.

[0048] In some embodiments, each radiating structure 210 includes eight arms having an Archimedes' spiral shape disposed between a respective inner ring and a respective outer ring (see above and FIG. 2B). Each arm of each radiating structure 210 may be coupled to a capacitor (e.g., capacitors 206A, 206B, 206C, and 206D) through the respective inner and outer rings. In other embodiments, the arms are electrically isolated from each other by slits or dielectric material.

[0049] The embodiment shown in FIG. 3A includes a mechanism for varying the resonant frequency of the outer zone segment with floating capacitor 208A using an externally mounted capacitor 402 and switch 406. Capacitor 402 and switch 406 are on the opposite side of insulating structure 204 from radiating structure 210. The resonant frequency of radiating structure 210 coupled to capacitor 208A is adjusted by opening and closing switch 406 between capacitor 402 coupled to ground and conductive plate 205 of capacitor 208A. Coupling and isolating capacitor 402 from ground, combining capacitor 402 with capacitor 208A, or operating capacitor 206A alone, changes the capacitance and therefore the impedance of the coupled radiating structure 210. This allows tuning or detuning the resonance of the coupled radiating structure 210 without changing the resonance of the other radiating structures 210, resulting in non-uniform current distribution to the various radiating structures 210. By varying the capacitance of the coupled radiating structure 210, the resonant frequency of the coupled radiating structure 210 can be shifted up or down, thereby increasing or decreasing the power coupled by the zone segment (e.g., the outer zone segment in FIG. 3A).

[0050] The switch 406 may be a semiconductor device such as a MOSFET (see below and FIGS. 3D-3E) or a SiC or GaN transistor controlled by a controller 404 (e.g., a processing unit such as a microprocessor with appropriate high-voltage control isolation). The switch may include an RF sinusoidal switch or a rectifying switch with a diode in parallel, a diode in series, or a combination thereof. The switching voltage may be less than 5 kV, e.g., in the range of 1 kV to 2 kV, which is suitable for solid-state switches (e.g., commercially available high-voltage semiconductor switching technology). These may be embedded in a printed circuit board (PCB) structure that may be mounted on the ground plane 202. Power regulation of the radiating structure can be performed by pulsing the switch 406. The switch 406 can be pulsed and synchronized with the pulsing of the supplied power to drive current to specific locations during a pulsed plasma process, such as forcing power to the center of the radiating structure 210 or the edge of the radiating structure 210. In some embodiments, a variable capacitor may be used instead of or in addition to the switch 406 and fixed capacitor 402.

[0051] The externally mounted capacitor 402 and switch may be implemented with discrete components, which is advantageous for facilitating service access. While Figure 3A shows capacitor 402 as being coupled to floating capacitor 208A of the outer zone segment, in other embodiments, capacitor 402 is coupled to a floating capacitor of an inner zone segment (e.g., capacitor 208C or 208D).

[0052] In various embodiments, two or more regions may each have their own respective capacitive circuit. Rotating plasma mixing can be achieved by pulsing the switches 406 coupled to each region in a rotating pattern. This rotating plasma mixing by pulsing the switches 406 in a rotating pattern can be used to implement a control scheme that smooths the generated plasma density in real time.

[0053] FIG. 3B illustrates an embodiment similar to that of FIG. 3A but with a capacitance circuit including a capacitor 408 that may be coplanar with the floating capacitor 206A of the outer zone segment. The capacitor 408 is formed by coupling another conductive plate 205 to the ground plane 202 across an insulating structure 204. The conductive plate 205 of the capacitor 408 may be fabricated from a unibody or segmented plate in the same process as the other conductive plates 205 of the outer and inner zones (e.g., capacitors 206A, 206B, 206C, and 206D). This may enable the capacitor 408 to be formed using cost-effective processes, such as printed circuit board manufacturing processes. The controller 404 is coupled to a switch 406 (e.g., a semiconductor device or mechanical method) that couples the conductive plate 205 of the capacitor 408 with the conductive plate of the capacitor 206A. The same side of the insulating structure 204 faces the switch 406 and the radiating structure 210. Although FIG. 3B shows capacitor 408 as being coupled to floating capacitor 208A of the outer zone segment, in other embodiments, capacitor 408 is coupled to a floating capacitor of an inner zone segment (e.g., capacitor 208C or 208D).

[0054] Figures 3C-3E show circuit diagrams of capacitive circuits for controlling the resonant frequency of antenna L2 (e.g., radiating structure 210, see above and Figures 3A-3B) in various closed and open states. Figure 3C shows a circuit diagram of a capacitive CLC circuit in which antenna L2 is coupled to a circuit having a first composite capacitor C5+C6 (e.g., capacitor 208A and capacitor 402, respectively) and a second composite capacitor C7+C8 (e.g., capacitor 208B and another capacitor 402, respectively).

[0055] 3D shows a circuit diagram of the capacitance circuit of FIG. 3C in which a first switch S1, coupling capacitor C5 in parallel with capacitor C6 to ground, is configured to be closed by controller 404, and a second switch S2, coupling capacitor C8 in parallel with capacitor C7 to ground, is configured to be closed by controller 404, thereby being in a closed state. The first switch S1 and the second switch S2 are shown as block diagrams that may represent any suitable switching devices (e.g., switches 406, such as semiconductor circuits or MOSFETs). In some embodiments, the first switch S1 and the second switch S2 are switching devices that may be configured to be on, off, 50% on, or other partial or variable on / off states.

[0056] FIG. 3E shows a circuit diagram of the capacitance circuit of FIG. 3C with the first switch S1 and the second switch S2 open so that capacitors C5 and C8 can be controlled in any manner. Opening and closing switches S1 and S2 can change the capacitance on each side of antenna L2. This shifts the resonant frequency of antenna L2 up or down, allowing the resonant frequency of one zone segment to be adjusted relative to the other. By adjusting the resonant frequencies of the zone segments relative to each other, plasma ignition at low pressures can be achieved, or the uniformity of plasma density during processing can be adjusted to account for the effects of chamber non-uniformity or non-uniformity across the wafer being processed. In some embodiments, switch S1 or switch S2 is pulsed (i.e., repeatedly opened and closed) to change the resonant frequency of antenna L2. In other embodiments, switches S1 and S2 are alternately pulsed to shift the resonant frequency of antenna L2, thereby transferring power coupling from antenna L2 to the plasma between the two sides of antenna L2.

[0057] FIG. 4A illustrates a multi-zone resonant structure 500 with inductive circuit control of the outer regions. The multi-zone resonant structure 500 is similar to the multi-zone resonant structure 400 described above. One or more mutual coupling coils 510 are positioned adjacent to a region or particular inductive segment (e.g., the outer region 312 or the inner region 322, see above and FIG. 2A ) to change the resonant frequency of the region through mutual coupling of magnetic fields from the radiating structures 210 via inductive coupling 520 between the mutual coupling coils 510 and the radiating structures 210. In the embodiment illustrated in FIG. 4A , the mutual coupling coils 510 are positioned adjacent to the two outer regions. However, any suitable number of mutual coupling coils 510 may be used to couple with the radiating structures 210 of any suitable number of outer or inner regions.

[0058] In some embodiments, the mutual coupling coil 510 is attached to a wall adjacent to the radiating structure 210, such as the conductive sidewall 202A extending downward from the ground plane 202. The mutual coupling coil 510 may be coupled to a controller 404, which may open and close a switch (see FIGS. 4B-4C below) to vary the inductive coupling 520. The mutual coupling coil 510 may be used to separately adjust the magnetic field generated by the radiating structure 210 by varying the magnetic field around the radiating structure 210 or a power driver circuit (not shown). Note that resonance with the mutual inductor may be implemented anywhere that can couple to an RF magnetic field in a localized region. For example, in the circuit diagram described below in connection with FIGS. 4B and 4C, any location physically close to the current path through antenna L2 and between capacitors C6 and C7 will create mutual coupling and shift the resonant frequency of antenna L2. This circuit is also not limited to a single inductor and may include additional RLC and semiconductor components intended to precisely control the selected region. This allows fine tuning of the generated plasma density to compensate for non-uniform chamber effects or wafer non-uniformities, or allows plasma ignition at lower pressures.

[0059] 4B-4C show circuit diagrams of an inductive circuit for controlling the power output of antenna L2 (e.g., radiating structure 210) in various closed and open states. FIG. 4B shows a circuit diagram of an inductive circuit in which antenna L2 is coupled to a CLC circuit having capacitor C6 (e.g., capacitor 208A) and capacitor C7 (e.g., capacitor 208A and another capacitor 402, respectively). An inductive loop (e.g., mutual coupling coil 510) having inductor M1′ is adjacent to the CLC circuit. Inductor M1′ is mutually coupled with inductor M1 between antenna L2 and capacitor C6. The inductive loop in FIG. 4B is in an open state by controller 404 setting third switch S3 (e.g., switch 406, such as a MOSFET) open so that inductor M1′ is coupled to ground on only one side. While the inductive loop is shown on the side of capacitor C6, another inductive loop (not shown) may exist on the side of capacitor C7.

[0060] The third switch S3 may be a transistor, such as a MOSFET device (see above and Figures 3D-3E), embedded or mounted in the wall of the structure (see above and Figure 4A) to control the coupling of inductor M1' to ground. Mounting the inductive circuit and control unit in the wall of the structure can provide further localization, which may improve circuit performance. The third switch S3 can be pulsed and synchronized with the pulsing of the supplied power to drive current to specific locations during a pulsed plasma process, such as forcing power to the edge of the radiating structure 210 or the center of the radiating structure 210. The magnetic flux-induced voltage due to the open inductive loop may be low enough to operate with commercial high-voltage switching technology (e.g., less than 5 kV, e.g., in the range of 1 kV to 4 kV).

[0061] FIG. 4C shows a circuit diagram of the inductive circuit of FIG. 4B with the third switch S3 closed, so that inductor L3 is coupled to ground on both sides, forming a grounded inductive loop. While inductor L3 replaces inductor M1' in FIG. 4B and inductor M1 is not shown in FIG. 4C, it should be understood that inductor L3 may be mutually coupled to part of the circuit between antenna L2 and capacitor C6. By opening and closing switch S3, the inductive coupling between antenna L2 and inductor L3 can be varied. This shifts the resonant frequency of antenna L2 up or down, allowing the power output of one region to be adjusted relative to other regions and zones. By adjusting the power output of the regions relative to each other, plasma ignition at low pressures can be achieved, or the uniformity of the plasma density during processing can be adjusted to account for the effects of non-uniform chamber conditions or non-uniformities in the wafer being processed.

[0062] FIG. 4D shows the frequency shift due to mutual induction coils adjacent to two regions. The mutual induction loops are enabled by forming closed loops that operate in grounded and open states. Trace 550 shows the frequency distribution from two regions, such as the first region and the second region, operating as a single system when the inductive loops adjacent to both the first region and the second region are open so that there is no mutual coupling (e.g., all antennas 362 operate as a single system, see above and FIG. 2B). Traces 560 and 570 show the frequency distribution when antenna 362 is configured in the first and second regions. Trace 560 shows the frequency distribution when the second region is enabled and the inductive loop adjacent to it is a grounded inductive loop. Trace 570 shows the frequency distribution when the first region is enabled and the inductive loop adjacent to it is a grounded inductive loop.

[0063] 5A-5B illustrate a control scheme for a plasma processing system according to some embodiments. FIG. 5A is a flowchart of a control scheme for a first region and a second region (e.g., region 312 and region 322, or a group of regions in the outer zone 310 radial set). A first region setting 630 is input to a first region controller 602, and a first region uniformity setting 632 is input to a first region uniformity controller 604. The first region controller 602 and the first region uniformity controller 604 may be processing units such as microprocessors. In some embodiments, the first region uniformity controller 604 is implemented as an additional control loop in the first region controller 602 and manages the uniformity adjustment using a sensor 620 for feedback.

[0064] The first zone settings 630 may include parameters for plasma generation, such as power, frequency, and modulation. The first zone uniformity settings 632 may include parameters for adjusting the resonant frequency and / or power of the first zone relative to another zone (e.g., the second zone). A sensor 620, such as a voltage-current (VI) sensor or an optical sensor, provides real-time feedback to the first zone controller 602 and the first zone uniformity controller 604 regarding the density and energy in the plasma chamber and the power supplied to the first zone.

[0065] The first region controller 602 and the first region uniformity controller 604 exchange data in real time to achieve the desired power and adjustments for the first region so that the plasma density shift is predictable. For example, if the first region controller 602 increases the power to the first region, the first region uniformity controller 604 can use the power increase to adjust the uniformity using frequency, power, or modulation adjustments so that a consistent percent shift is maintained across the power increase.

[0066] The first region controller 602 generates an output 640, which may include parameters such as power, frequency, and modulation, to control a power source (e.g., RF source 102, see above and FIG. 1A) for the first region. In some embodiments, the power source includes a power amplifier that receives instructions from the output 640. The first region uniformity controller 604 generates a uniformity output 642 to control switches in a capacitive or inductive circuit to define the first region.

[0067] The second region may have a similar control scheme as the first region, with the second region controller 612 being similar to the first region controller 602 and the second region uniformity controller 614 being similar to the first region uniformity controller 604. The second region controller 612 receives a second region setting 650 and the second region uniformity controller 614 receives a second region uniformity setting 652, which are similar to the first region setting 630 and the first region uniformity setting 632, respectively. A sensor 620 provides feedback to the second region controller 612 and the second region uniformity controller 614, which exchange data with each other in real time. The second zone controller 612 generates an output 660, and the second zone uniformity controller 614 generates a zone output 662 to control the power supply for the second zone and the switches in the capacitive or inductive circuits to define the second zone, respectively. The first zone setting 630, the first zone uniformity setting 632, the second zone setting 650, and the second zone uniformity setting 652 may be provided by a controller for the overall multi-zone system, such as controller 702 (see below and FIG. 5B).

[0068] FIG. 5B is a control diagram of a control scheme 700 for a multi-zone resonant structure, according to some embodiments. A controller 702 provides settings in real time to a module controller 718 for each region. The module controller 718 then applies the settings to a power supply 720, which supplies power to each region and may pulse switches in capacitive or inductive circuits to achieve the desired plasma density. The power supply 720 may be an inductively coupled plasma (ICP) source or a capacitively coupled plasma (CCP) source. In some embodiments, the CCP source is divided into segments, and the resonant control of each CCP source segment is excited by mutually coupled coils, such as the ICP antenna described above in connection with FIGS. 4A-4C.

[0069] In some embodiments, the controller 702 is a machine learning (ML)-based controller, such as a microprocessor configured to implement a live machine learning mode. The controller 702 includes a local pulse controller 704 and a local electronic switching controller 706. The local pulse controller 704 and the local electronic switching controller 706 may be similar to the first regional controller 602 and the first regional uniformity controller 604, respectively, described above in connection with FIG. 5A. The local pulse controller 704 and the local electronic switching controller 706 may exchange local settings in real time to control plasma density shifts.

[0070] The local pulse controller 702 receives inputs from area sensors, including one or more zone VI sensor(s) 708, RF VI sensor(s) 710, optical sensor(s) 712, and RF power sensor(s) 714. Optical measurements from the optical sensor(s) 712 can be used for plasma density feedback control. The area VI sensor(s) 708 can provide a powerful regulated feedback control signal, which can be combined with the forward and reflected power from the RF VI sensor(s) 710 for a robust set of multiple inputs for feedback control. The controller 702, configured to run live machine learning models, can use the feedback from the sensors to map chamber condition changes (such as changes in power, pressure, and chemistry) from process step to process step. This can maintain uniformity across process steps, wafer-to-wafer, and chamber clean lifecycles.

[0071] FIG. 6 is a graph illustrating plasma ignition at low pressures by focusing power on a single region (e.g., one or more composite regions 312 or 322, see above and FIG. 3A). Focusing power on a single region can enable plasma ignition at extremely low pressures and allows predictable and repeatable control of the location of ignition. As power is biased toward the resonant region(s), the voltage on the antenna(s) in the region increases until the electric field at the dielectric top (e.g., dielectric plate 114, see above and FIG. 1A) triggers a plasma discharge, igniting the plasma. After plasma ignition, power can be adjusted between regions to achieve a desired plasma density, such as a uniform plasma density.

[0072] In FIG. 6, trace 752 is the voltage at the antenna in the region, trace 754 is the reflected power measured at the power supply, trace 756 is the output of the photodiode sensor, and dashed line 758 is the time at which ignition occurred. At time zero, the voltage at the antenna is ramped up, and the reflected power increases with the voltage until the reflected power has an inflection resonance and then drops sharply. The voltage peaks at ignition and can then be lowered to maintain the plasma. The photodiode signal increases from zero at ignition as measurement of light from the ignited plasma begins. In some embodiments, ignition occurs after a time ranging from 2 μs to 100 μs, e.g., 6.3 μs, after the start of the voltage ramp-up. In some embodiments, the peak voltage at ignition is in the range of 50 V to 4000 V, e.g., 556 V.

[0073] 6, argon gas is ignited into a plasma at a pressure of 0.267 mTorr. However, any suitable gas may be used for the plasma, such as oxygen (O), nitrogen (N), hydrogen (H), neon, krypton, C4F8, HBr, Cl, SF6, etc., or combinations thereof. The plasma can be ignited at very low pressures, for example, in the range of 0.2 mTorr to 1000 mTorr.

[0074] 7A-7C illustrate a plasma power pulse recipe having three phases (i.e., power levels) for plasma processing, according to some embodiments. Figure 7A shows the average applied power per phase graphed against time.

[0075] FIG. 7B illustrates an example of RF pulsing for each region of a multi-zone resonant structure, in which the power from the pulse recipe of FIG. 7A is allocated between two regions to generate a three-phase pulse pattern with a period of 2180 microseconds (μs). The three-phase pulse pattern has a first phase of 860 μs at high power, a second phase of 680 μs at medium power, and a third phase of 620 μs at power off. FIG. 7B illustrates an example of using the sub-pulse control method for plasma processing using a two-step square wave graphed as applied power over time as in FIG. 7A. It should be appreciated that the waveform in FIG. 7B is a non-limiting example, and any suitable waveform can be used for pulsed plasma processing. As an example, in a multi-zone resonant structure with eight zone segments, Region 1 includes seven antenna segments, and Region 2 includes the remaining antenna segments. As shown in FIG. 7B, the delivered pulse power of the recipe alternates between Region 1 and Region 2 during each sub-pulse of the three-phase pulse pattern. In the example of Figure 7B, the power supplied to region 2 is less than the power supplied to region 1. However, any suitable allocation of power between regions 1 and 2 may be used, such as multi-tone power where two or more frequencies and amplitudes are combined.

[0076] FIG. 7C shows an exemplary recipe for RF pulsing by region, similar to the recipe of FIG. 7B but including a plasma ignition step. The applied power by region is graphed versus time. The plasma density versus time is also shown. As shown in FIG. 7C, each pulse begins with a much higher power allocation to region 2 to ignite the plasma. After plasma ignition, the recipe returns to the alternating pattern of FIG. 7B, where region 1 receives a significantly greater amount of power than region 2. As an example, during ignition, region 2 receives a first amount of power, region 1 receives a second amount of power that is less than the first amount of power, and after ignition, region 2 receives a third amount of power, and region 1 receives a fourth amount of power that is greater than the third amount of power. As another example, during ignition, region 2 receives a greater areal density of power than the areal density of power supplied to region 1 during ignition (in other words, with more electrical or inductive power supplied to a smaller area), and after ignition, region 2 receives the same or a lesser areal density of power as the power supplied to region 1. The areal density of power supplied to region 2 during ignition can be greater than the areal density of power supplied to region 1 during ignition, even if the total amount of power supplied to region 1 is greater than the total amount of power supplied to region 2 during ignition.

[0077] In some embodiments, power is supplied to Region 1 and Region 2 by discretely pulsing power between a first frequency and a second frequency, where the first frequency is closer to the resonant frequency of the first region and the second frequency is closer to the resonant frequency of the second region, such that power supplied at the first frequency couples into the first region and power supplied at the second frequency couples into the second region.

[0078] Figures 8A-10B are schematic diagrams of example circuits for multi-region inductively coupled plasma (ICP) systems with various numbers of regions. Figures 8A-8B show example circuits for an ICP system configurable for two regions, Figure 9 shows example circuits for an ICP system configurable for three regions, and Figures 10A-10B show example circuits for an ICP system configurable for eight regions. The regions can be configured to function together as a single region or as multiple regions, each with one or more antenna circuits. Each region can be power balanced using a peak power priority during ignition and an average power priority set for one end of the region's antenna(s). Antennas arranged in a radial pattern, such as an Archimedes spiral (see above and Figure 2B), can control the balance and enable radial power distribution (also known as radial control).

[0079] 8A is a circuit diagram of an example circuit for a two-antenna ICP system that can be configured to function as one or two regions. The example circuit includes an antenna A1 for the first region and an antenna A2 for the second region. Antenna A1 is coupled to ground across Zmc circuits Zmc1 and Zmc2, and antenna A2 is coupled to ground across Zmc circuits Zmc3 and Zmc4.

[0080] The circuit further includes an impedance control circuit, also referred to as a Z circuit, between each end of the antenna segment and the Zmc circuit. The Zmc circuits Zmc1-Zmc4 can interact with each other through mutual inductance, by changing capacitance, or by directly changing impedance (i.e., increasing or decreasing capacitance) to shift the resonance of one end of antennas A1 and A2. The Zmc circuits can be short or open circuits. Changing the value (e.g., capacitance or inductance) of each Zmc circuit controls the frequency of the antenna (e.g., antenna A1 or A2) by controlling how much power is coupled into the antenna. This can change the balance of power distributed between the regions after the first ignition pulse (e.g., changing the power balance in the pulse between regions 1 and 2 after ignition, see above and FIG. 7C). Changing the value of the Zmc circuit can be done electronically (e.g., with a voltage-adjusting capacitance of a varactor) or mechanically (e.g., by adjusting the distance between the parallel plates of a capacitor).

[0081] The nodes between antennas A1 and A2 and the Zmc circuit are coupled via Z circuits Z1 and Z2. The Z circuits represent inductive or capacitive circuits that can be arranged as parallel or series LRC circuits. These circuit elements control the power and current balance between the regions and affect the resonant frequencies of the regions. The LRC circuits can be open or short circuits. The Z circuit values ​​(e.g., capacitance or inductance) can be electronically or mechanically adjustable. The Z circuits can include diodes and controllable semiconductor devices. The Z circuits Z1 and Z2 can be set to closed to operate the two antennas as one region, or the Z circuits Z1 and Z2 can be set to open to operate the two antennas as two independent regions.

[0082] FIG. 8B is a circuit diagram of the circuit of FIG. 8A showing the internal components of the Zmc circuit, according to one embodiment. The Zmc1 circuit includes a capacitor C1 and a Zc1 circuit, which are coupled in parallel between ground and a node between the antenna A1 and the Z1 circuit. A loop including the Zm1 circuit and an inductor M1 is coupled to an inductor M1' (such as a supporting metal conductor) between the capacitor C1 and the antenna A1. The Zc1 circuit can be used to adjust capacitance through its parallel capacitance with the capacitor C1, and the Zm1 circuit can be used to adjust inductance through its mutual inductance with the inductor M1. Similarly, the other Zmcx circuits each include a respective capacitor Cx, Zcx circuit, Zmx circuit, and inductors Mx and Mx' in a similar arrangement, where x is a number between 2 and 4.

[0083] Figure 9 is a schematic diagram of an example circuit for a three-antenna ICP system that can be configured to function as one, two, or three regions by opening or closing appropriate Z-circuits. The circuit in Figure 9 is similar to that of Figure 8A, but adds a third antenna A3, whose ends are coupled to ground by Zmc circuits Zmc5 and Zmc6. Z-circuits Z3 and Z4 couple antenna A3 to antenna A2, and Z-circuits Zn1 and Zn2 couple antenna A3 to antenna A1. Antenna A3 (or antenna A8 or any other final antenna, see below and Figures 10A-10B) may be physically adjacent to antenna A1, such as when antennas A1-A3 are spiral arms of an antenna structure with n-fold symmetry (see above and Figure 2B).

[0084] FIG. 10A is a schematic diagram of an exemplary circuit for an eight-zone ICP system configured to function as one zone when all Z circuits are closed. The circuit in FIG. 10A is similar to the circuit in FIG. 9, but adds antennas A3-A8, Zmc circuits Zmc7-Zmc16, and Z circuits Z5-Z14. Z circuits Zn1 and Zn2 couple antenna A8 to antenna A1. While the circuit in FIG. 10A is shown configured to function as one zone, it may be configured to function as any of two to eight zones by opening or closing the appropriate Z circuits.

[0085] FIG. 10B is a circuit diagram of the example circuit of FIG. 10A for an eight-zone ICP system configured to function as two regions when circuits Z1-Z4 (see above and FIG. 10A) are open. Region 1 includes antennas A1 and A4-A8, Z circuits Z7-Z14, Zf1, and Zf2, and Zmc circuits Zmc1, Zmc2, and Zmc7-Zmc16. Region 2 includes antennas A2 and A3, Z circuits Z3 and Z4, and Zmc circuits Zmc3-Zmc6. In some embodiments, power is focused on Region 2 at the beginning of the pulse to achieve plasma ignition, and then power alternates between Regions 1 and 2 (see above and FIG. 7C).

[0086] 11 is a process flow diagram of a method 800 for plasma processing, according to some embodiments. Step 802 is the start of a process recipe for a wafer (e.g., substrate 110), which is placed in the plasma chamber 106 as described above with respect to FIG. 1A. In step 804, a check is made (e.g., by controller 702, see above and FIG. 5B) whether low-pressure plasma ignition is desired, such as by checking user-set parameters for low-pressure plasma ignition. If low-pressure plasma ignition is desired, the method proceeds to step 806; if low-pressure plasma ignition is not desired, the method proceeds to step 808.

[0087] In step 806, the controller 702 configures the recipe regions (e.g., regions 1 and 2, see above and FIG. 10B) with ignition pulse patterns, as described above in connection with Figures 6 and 7C. In step 808, the controller 702 configures the recipe regions for uniformity control across the regions (e.g., with balanced power distribution across the regions, such as by rotating plasma mixing), as described above in connection with Figure 3A.

[0088] In step 810, the controller 702 executes a recipe, which may include low-pressure ignition followed by plasma uniformity control, as described above in connection with Figures 5A-5B. In step 812, the controller 702 executes real-time uniformity control using real-time plasma uniformity measurements, as described above in connection with Figures 5A-5B. Finally, in step 814, the wafer recipe is complete and the wafer (e.g., substrate 110) may be removed from the plasma chamber 106 or may be further processed using additional recipes in situ.

[0089] 12 is a process flow diagram of a method 900 for plasma processing, according to some embodiments. In step 902, a substrate 110 is loaded into a plasma processing system 100, as described above in connection with FIG. 1A. The plasma processing system includes a multi-zone resonant structure 300 (see above and FIG. 2A) including a first region (e.g., region 2, see above and FIG. 7C) and a second region (e.g., region 1, see above and FIG. 7C) adjacent to the first region.

[0090] In step 904, a plasma is ignited by supplying a first amount of power to a first region and a second amount of power to a second region, the first amount of power being greater than the second amount of power, as described above with reference to Figure 7C. In step 906, a plasma process is performed on the substrate 110, as described above with reference to Figure 7C. The plasma process includes generating a uniform density plasma by supplying a third amount of power to the first region and a fourth amount of power to the second region, the third amount of power being less than the fourth amount of power.

[0091] Adjusting the power delivered to the plasma by zone (e.g., by azimuthal and / or radial zone segment) can compensate for chamber uniformity due to changes in gas flow, antenna non-uniformity, or power return through the chamber walls or RF path, which may change after disassembly and assembly of the plasma processing device. For example, adjusting the delivered plasma power non-uniformity can compensate for chamber changes that occur during a wet cleaning process. Adjusting the delivered plasma power non-uniformity can also enable chamber-to-chamber matching to achieve the same plasma uniformity between process chambers with different non-uniformities.

[0092] In embodiments with segmented antennas, the antennas in different radial zones can be raised or lowered to change the radial diameter and strength, thereby varying the coupling area. Vertical adjustment can reduce unwanted local sputtering from the dielectric area of ​​the top plate. The larger gap allowed by vertically adjusting the antenna position reduces capacitive coupling between the antenna and the generated plasma.

[0093] In some embodiments, the antenna is radially rotated to rotate the generated plasma. Resonant hot spots can occur due to constant impedance paths in the power flow in the process chamber. Rotating the antenna can prevent or reduce the plasma from being drawn into the resonant hot spots, thereby reducing unwanted partial sputtering from the dielectric region of the top plate.

[0094] In some embodiments, controlling plasma uniformity can achieve plasma ignition at lower pressures, for example, by switching on one azimuthal zone, allowing for more power to be delivered in a smaller area. Ignition can be achieved through high capacitive coupling when the antenna is in close proximity to a dielectric structure between the antenna and the process chamber (e.g., dielectric plate 114, see above and FIG. 1A). Additionally, activating one zone segment can allow a greater amount of power to be focused into one spot to achieve ignition. After plasma ignition, the remaining zones can be turned on, if necessary, to achieve a more uniformly dense plasma.

[0095] Real-time control can balance power distribution by active measurement of plasma density per zone segment by optical or current or field measurements. Balancing power distribution in real time can control plasma impedance to produce desired shifts in plasma density. Radial and azimuthal control can be achieved by shifting the location of power coupling under the inductively coupled plasma (ICP) antenna.

[0096] Plasma uniformity measurements can be performed by measuring the current in the capacitor of the area using the relationship of current to capacitance and voltage in the case of capacitive circuit control:

number

[0097] Optical measurements of radial and azimuthal plasma density can be performed by optical sensors located on the top surface of a dielectric structure (e.g., dielectric plate 114, see above and FIG. 1A) near the primary power coupling area of ​​the antenna. The optical sensors can include photodiodes, charge-coupled device (CCD) cameras, etc., or combinations thereof. The optical sensors can be located at remote locations outside the RF field. Light transmission to the optical sensors can be achieved by using fiber optic bundles, light pipes, or light tubes between the optical sensors and the device to reduce light emission losses. Optical camera images with wide-angle pickup can be implemented by using multiple optical cameras so that the images overlap, combining the images (e.g., by using intensity and / or color matching), and subtracting the antenna structure from the combined image.

[0098] Optical sensors can be combined with pulse control to enable density measurements in radial or azimuthal regions and calculate delivered power balance by detecting pulse waveforms, including ignition time delays, ramp times, pulse peaks and valleys, and total pulse area. One or more optical sensors may be used to detect pulse waveforms. Pulse optical responses can be measured between radial and azimuthal regions. For example, optical sensors can measure pulse shapes at multiple locations (e.g., 1 to 100 locations) to enable plasma uniformity control by controlling and adjusting radiant power per region. An example of a single-location optical sensor is a CCD camera with a pickup larger than one area, which can measure the gradient of average or peak intensity across an area. An example of an optical sensor with 100 locations is an array of fiber optic sensors, which can be combined across a CCD array or photodiode array. Optical sensors can measure pulse shape data, such as the shape of the pulse with steady-state intensity or the pulse ignition delay.

[0099] In some embodiments, a multi-zone resonant structure (also called a resonant antenna system) has two or more control regions. The multi-zone resonant structure can have any suitable configuration of radial and / or azimuthal zones. The multi-zone resonant structure can have a rectangular source or a bias or focus ring plasma source. In some embodiments, the antennas of the multi-zone resonant structure are segmented into groups that can include adjacent antennas or separate antenna regions. Power balance across the regions of the multi-zone resonant structure can be achieved by controlling the resonant frequency between each region. The frequency spectrum of the supplied power can include single or multiple sinusoids (also called "tones") or can have a mixture of broadband RF (also called multi-frequency RF). Because the regions can be set to different resonant frequencies, the power balance to each region can be controlled by applying power at one or more frequencies to select the regions. This control over the amount of power distributed to the resonant regions allows for adjustment of plasma uniformity (by matching the resonant frequencies of the regions). Local plasma density can be adjusted by applying power per unit time control delivered through frequency, amplitude, and pulse duration. The power absorbed in each region is controlled by an impedance control (e.g., Z circuit and Zmc circuit) in each region, which sets the frequency and bandwidth of the power absorbed in each region. The Z circuit is coupled between the antennas, and the Zmc circuit is coupled to the ends of the antennas. Power can be applied to specific regions using pulse modulation with pulse steps. One or more optical intensity measurements of the plasma can be used for one or more regions for feedback control. One or more RF measurements (e.g., voltage or current measurements) can be used for each region for feedback control to achieve power balance between the regions. In some embodiments, feedback control combines optical intensity and RF measurements.

[0100] Local segmentation control can be achieved by configuring impedance control of one or more antennas. In some embodiments, local segmentation control is achieved by controlling Z circuits, Zmc circuits, or both Z and Zmc circuits between antennas. In some embodiments, power balance along the antenna (e.g., power balance between the center and edge of the antenna) is achieved by controlling Zmc circuits, Z circuits, or both Zmc and Z circuits coupled to the end of each antenna.

[0101] The specific region for plasma ignition (e.g., the area or specific location in the plasma chamber where the plasma is initially ignited) can be determined by configuring impedance control elements (e.g., Z circuits and Zmc circuits) for the desired antenna to absorb power. The location of plasma ignition can be controlled by controlling the frequency of the supplied power and the resonant frequency of the antenna.

[0102]

[0023] Exemplary embodiments of the present disclosure are summarized here. Other embodiments may be understood from the claims of this application, as well as from the entire specification.

[0103] Example 1. 1. An apparatus for plasma processing comprising: an RF power source; and a set of resonant structures coupled to the RF power source, the resonant structures comprising: a first region comprising a first antenna and a first coupling circuit outside of a coupling of the RF power source to the first region, the first coupling circuit being configured to adjust power distribution in the first region; and a second region adjacent to the first region, the second region comprising a second antenna.

[0104] Example 2. 10. The apparatus of Example 1, wherein the first coupling circuit is a capacitive coupling circuit, the capacitive coupling circuit comprising a capacitor coupled to ground across a switch.

[0105] Example 3. 3. The apparatus of example 2, wherein the switch is a semiconductor device.

[0106] Example 4. 4. The apparatus of Example 2 or 3, wherein a resonant structure of the set of resonant structures further comprises an insulating structure, a first side of the insulating structure facing the first antenna.

[0107] Example 5. 5. The device of example 4, wherein the first side of the insulating structure faces the switch.

[0108] Example 6. 5. The apparatus of example 4, wherein the switch is on a second side of the insulating structure, the second side being opposite the first side.

[0109] Example 7. 10. The apparatus of Example 1, wherein the first coupling circuit is an inductive coupling circuit, the inductive coupling circuit comprising a mutual coupling coil.

[0110] Example 8. 8. The apparatus of any one of Examples 1-7, further comprising: a controller coupled to the first coupling circuit, the controller configured to control the first coupling circuit; and a sensor coupled to the controller, the sensor providing real-time feedback to the controller.

[0111] Example 9. The device of example 8, wherein the sensor is a voltage sensor.

[0112] Example 10. The device of example 8, wherein the sensor is an optical sensor.

[0113] Example 11. 1. An apparatus for plasma processing comprising: a resonant structure having a cylindrical or axisymmetric shape, the resonant structure comprising a plurality of azimuthal regions, a first azimuthal region of the plurality of azimuthal regions comprising a first antenna and a first impedance control circuit coupled to the first antenna, the first impedance control circuit being configured to shift a resonance of one end of the first antenna, and a second azimuthal region of the plurality of azimuthal regions comprising a second antenna and a second impedance control circuit coupled to the second antenna.

[0114] Example 12. 12. The device of example 11, wherein the first impedance control circuit is electronically or mechanically adjustable.

[0115] Example 13. 13. The apparatus of any one of Examples 11 to 12, wherein the first antenna and the second antenna are electrically coupled to each other via a third impedance control circuit.

[0116] Example 14. 14. The device of example 13, wherein the coupling between the first antenna and the second antenna is electrically or mechanically controllable.

[0117] Example 15. 13. The device of any one of Examples 11 to 12, wherein the first antenna and the second antenna are part of a unibody antenna.

[0118] Example 16. 13. The device of example 11 or 12, wherein the first antenna and the second antenna are electrically isolated from each other.

[0119] Example 17. 1. A method for plasma processing, comprising: loading a substrate into a plasma processing system, the plasma processing system comprising a multi-region resonant structure, the multi-region resonant structure comprising a first region and a second region adjacent to the first region; igniting a plasma by supplying a first amount of power to the first region and a second amount of power to the second region, the first amount having a greater areal density than the second amount; and performing a plasma process on the substrate, the plasma process comprising generating a plasma of uniform density.

[0120] Example 18. 18. The method of Example 17, wherein performing the plasma process further includes supplying power to the first region at a first frequency while varying a resonant frequency of the antenna in the first region by pulsing a first switch coupled to a first side of the antenna.

[0121] Example 19. 18. The method of Example 17, wherein performing the plasma process further comprises discretely pulsing power between a first frequency and a second frequency, the first frequency being closer to a resonant frequency of the first region and the second frequency being closer to a resonant frequency of the second region.

[0122] Example 20. 20. The method of any one of Examples 17-19, wherein generating a uniform density plasma comprises rotating plasma mixing.

[0123] While the present invention has been described with reference to exemplary embodiments, this specification 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 invention, will be apparent to those skilled in the art upon reading this specification. It is therefore intended that the appended claims cover any and all such modifications or embodiments.

Claims

1. an RF power source; a set of resonant structures coupled to the RF power source, the resonant structures comprising: A first region, a first antenna; a first coupling circuit outside of the coupling of the RF power source to the first region, the first coupling circuit configured to adjust the power distribution of the first region; and a first region comprising: a second region adjacent to the first region, the second region comprising: Second Antenna a second region comprising: a set of resonant structures comprising: An apparatus for plasma processing comprising:

2. 2. The apparatus of claim 1, wherein the first coupling circuit is a capacitive coupling circuit, the capacitive coupling circuit comprising a capacitor coupled to ground across a switch.

3. The apparatus of claim 2 , wherein the switch is a semiconductor device.

4. 3. The apparatus of claim 2, wherein a resonant structure of the set of resonant structures further comprises an insulating structure, a first side of the insulating structure facing the first antenna.

5. The apparatus of claim 4 , wherein the first side of the insulating structure faces the switch.

6. 5. The apparatus of claim 4, wherein the switch is on a second side of the insulating structure, the second side being opposite the first side.

7. The apparatus of claim 1 , wherein the first coupling circuit is an inductive coupling circuit, the inductive coupling circuit comprising a mutually coupled coil.

8. a controller coupled to the first coupling circuit, the controller configured to control the first coupling circuit; a sensor coupled to the controller, the sensor providing real-time feedback to the controller; and The apparatus of claim 1 further comprising:

9. The apparatus of claim 8 , wherein the sensor is a voltage sensor.

10. The apparatus of claim 8 , wherein the sensor is an optical sensor.

11. A resonant structure having a cylindrical or axisymmetric shape, the resonant structure comprising: a plurality of azimuthal regions, a first azimuthal region of the plurality of azimuthal regions comprising a first antenna and a first impedance control circuit coupled to the first antenna, the first impedance control circuit configured to shift a resonance of one end of the first antenna, and a second azimuthal region of the plurality of azimuthal regions comprising a second antenna and a second impedance control circuit coupled to the second antenna; a resonant structure comprising: An apparatus for plasma processing comprising:

12. 12. The apparatus of claim 11, wherein the first impedance control circuit is electronically or mechanically adjustable.

13. The apparatus of claim 11 , wherein the first antenna and the second antenna are electrically coupled to each other via a third impedance control circuit.

14. 14. The apparatus of claim 13, wherein the coupling between the first antenna and the second antenna is electrically or mechanically controllable.

15. The device of claim 11 , wherein the first antenna and the second antenna are part of a unibody antenna.

16. The apparatus of claim 11 , wherein the first antenna and the second antenna are electrically isolated from each other.

17. loading a substrate into a plasma processing system, the plasma processing system comprising a multi-region resonating structure, the multi-region resonating structure comprising a first region and a second region adjacent to the first region; igniting a plasma by supplying a first amount of power to the first region and a second amount of power to the second region, the first amount having a greater areal density than the second amount; performing a plasma process on the substrate, the plasma process including generating a uniform density plasma; 1. A method for plasma processing, comprising:

18. 20. The method of claim 17, wherein performing the plasma process further comprises supplying power to the first region at a first frequency while varying a resonant frequency of the antenna in the first region by pulsing a first switch coupled to a first side of an antenna.

19. 20. The method of claim 17, wherein performing the plasma process further comprises discretely pulsing power between a first frequency and a second frequency, the first frequency being closer to a resonant frequency of the first region and the second frequency being closer to a resonant frequency of the second region.

20. The method of claim 17 , wherein generating the plasma of uniform density comprises rotating plasma mixing.

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