Radio frequency electrostatic chuck filter circuit

Abstract

Embodiments described herein relate to devices and methods for substantially reducing the occurrence of radio frequency (RF) coupling by chucking electrodes. A chucking electrode is disposed in an electrostatic chuck positioned on a substrate support. The substrate support is coupled to the process chamber body. The RF source is used to generate plasma in a process volume adjacent to the substrate support. An impedance matching circuit is disposed between the RF source and a chucking electrode disposed in the electrostatic chuck. An electrostatic chuck filter is coupled between the chucking electrode and the chucking power source.

Description

[0001] This application is a divisional application of a Chinese patent application (PCT application number PCT / US2020 / 018512) with an application date of February 17, 2020, an application number of 202080029359.5, and a title of "Radio Frequency Electrostatic Chuck Filter Circuit". Technical Field

[0002] Embodiments of the present disclosure generally relate to semiconductor processing, and more particularly to apparatuses and methods for generating and controlling radio frequency (RF) plasmas for thin film deposition. Background Art

[0003] In the fabrication of integrated circuits, deposition processes such as chemical vapor deposition (CVD) are commonly used to deposit films of various materials on a substrate. For example, in plasma enhanced chemical vapor deposition (PECVD), electromagnetic energy is applied to at least one precursor gas or vapor to generate a plasma.

[0004] In some examples, the electromagnetic energy used to generate the plasma can be radio frequency (RF) power. However, when RF power is used, capacitive coupling occurs between the plasma and the clamping electrode in the electrostatic chuck. The capacitive coupling results in RF coupling that induces high RF voltages and currents on and through the clamping electrode, which causes power loss and damage to the power supply of the clamping electrode.

[0005] Accordingly, there is a need for improved apparatuses and methods for RF power application. Summary of the Invention

[0006] In one embodiment, an apparatus is provided that includes a chamber body and a lid, the chamber body and the lid defining a process volume within the chamber body and the lid. A substrate support is disposed within the process volume. A first electrode is embedded within the substrate support. A radio frequency (RF) source is coupled to the first electrode. An impedance matching circuit is disposed between the RF source and the first electrode. A second electrode is embedded within the substrate support. A power source is coupled to the second electrode. An electrode filter is disposed between the second electrode and the power source and is coupled to the second electrode and the power source.

[0007] In another embodiment, a device is provided that includes a chamber body and a lid, where the chamber body and the lid define a process volume within the chamber body and the lid. A gas distribution plate is disposed within the process volume and positioned adjacent to the lid. A substrate support is disposed within the process volume. A first electrode is embedded within the substrate support. A radio frequency (RF) source is coupled to the first electrode. An impedance matching circuit is disposed between the RF source and the electrode. A second electrode is embedded within the substrate support. A power source is coupled to the second electrode. An electrode filter is disposed between the second electrode and the power source. The electrode filter includes: a first inductor that is coupled to the second electrode. A second inductor is provided in series with the first inductor. A third inductor is provided in series with the first inductor and the second inductor. A resistor is provided in series with the first inductor, the second inductor, and the third inductor. The resistor is coupled to the power source, and a first capacitor is provided in parallel with the second inductor.

[0008] In yet another embodiment, a device is provided that includes a chamber body and a lid, where the chamber body and the lid define a process volume within the chamber body and the lid. A gas distribution plate is disposed within the process volume and positioned adjacent to the lid. A substrate support is disposed within the process volume. A first electrode is embedded within the substrate support. A second electrode is embedded within the substrate support between the first electrode and the surface of the substrate support facing the lid. A radio frequency (RF) source is coupled to the first electrode. An impedance matching circuit is disposed between the RF source and the first electrode. A power source is coupled to the second electrode. An electrode filter is disposed between the second electrode and the power source. The electrode filter includes: a first inductor that is coupled to the second electrode; a second inductor in series with the first inductor; a third inductor in series with the first inductor and the second inductor; and a resistor in series with the first inductor, the second inductor, and the third inductor. The resistor is coupled to the power source. The electrode filter also includes: a first capacitor that is in parallel with the second inductor; a first ground path that is coupled to the electrode filter between the second inductor and the third inductor; and a second ground path that is coupled to the electrode filter between the third inductor and the resistor. The first ground path includes a second capacitor. The second ground path includes a third capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to understand the above features of the present disclosure in a detailed manner, the present disclosure may be described more specifically by referring to embodiments, the description of which has been briefly summarized above, and some of which are shown in the accompanying drawings. However, it should be noted that the drawings only show exemplary embodiments and should not be considered as limiting its scope, since the present disclosure may allow other equivalent embodiments.

[0010] Figure 1 is a schematic view of a process chamber according to one embodiment.

[0011] Figure 2A is a schematic representation of a filter circuit according to one embodiment.

[0012] Figure 2B is a schematic representation of a filter circuit according to one embodiment.

[0013] Figure 3 is a schematic representation of an impedance matching circuit according to one embodiment.

[0014] Figure 4 is a plan view of a cluster tool device according to one embodiment described herein.

[0015] For ease of understanding, the same reference numerals are used to label the same elements common to the drawings as much as possible. It is contemplated that the elements and features of one embodiment may be beneficially incorporated into other embodiments without further recitation. Detailed Description

[0016] The embodiments described herein relate to devices and methods for substantially reducing the occurrence of radio frequency (RF) coupling through clamping electrodes. The clamping electrodes are disposed in a substrate support, which is coupled to a process chamber body. An RF source is used to generate a plasma in a process volume adjacent to the substrate support. An impedance matching circuit is disposed between the RF source and the clamping electrodes disposed in the substrate support. To reduce damage to the clamping electrodes and the clamping power source coupled thereto, an electrostatic chuck filter is coupled between the clamping electrodes and the clamping power source.

[0017] Figure 1FIG. 0 is a schematic view of a process chamber 100 according to one embodiment. The process chamber 100 includes a chamber body 102 and a lid 104, and the chamber body 102 and the lid 104 define a process volume 120 within the chamber body 102 and the lid 104. A substrate support 114 and a gas distribution plate 108 are disposed within the process volume 120. The substrate support 114 is supported within the chamber body 102 via a rod 106. The substrate support 114 includes one or more conductive plates, insulating plates, device plates, cooling channels, etc. to facilitate substrate processing. In one embodiment, the rod 106 is substantially orthogonal to the lid 104 and is coupled to the chamber body 102 opposite the lid 104, or is disposed through an opening in the chamber body 102 opposite the lid.

[0018] In one embodiment combinable with one or more of the above embodiments, the substrate support 114 is made of an aluminum-containing material. For example, the substrate support 114 may be made of aluminum nitride material. An electrostatic chuck 115 may be positioned on the upper surface of the substrate support 114 to facilitate clamping of the substrate during processing. The electrostatic chuck 115 includes electrodes 122 disposed within the electrostatic chuck 115. In one embodiment combinable with one or more of the above embodiments, the electrodes 122 are conductive grids.

[0019] The upper surface 116 of the electrostatic chuck 115 may have a plurality of raised portions (not shown) formed thereon. The raised portions may contact a substrate (not shown) disposed on the upper surface 116 of the electrostatic chuck 115. Gas may flow between the substrate and the surface 116 of the electrostatic chuck 115 and / or between the substrate support 114 and the lower surface of the electrostatic chuck to maintain thermal equilibrium between the substrate and the substrate support 114. In such an example, the fluid temperature may be controlled, for example, via a heat exchanger.

[0020] The gas distribution plate 108 is coupled to the chamber body 102. An air chamber 110 is defined between the lid 104 and the gas distribution plate 108. The gas distribution plate 108 is disposed opposite the substrate support 114. A plurality of holes 112 are formed through the gas distribution plate 108. The plurality of holes 112 are distributed across the gas distribution plate 108 to facilitate inflow of process gas into the process volume 120.

[0021] A gas delivery system 126 is coupled to the lid 104 via a delivery line 128. The gas delivery system 126 supplies one or more gases to the process chamber 100 to process a substrate disposed therein. When one or more gases enter the process chamber 100 through the lid 104, the gases enter the air chamber 110 and flow through the plurality of holes 112 in the gas distribution plate 108. The plurality of holes 112 distribute the gases radially across the surface 116 of the electrostatic chuck 115.

[0022] Electrode 118 is embedded in substrate support 114. Radio frequency (RF) power is provided to electrode 118 via RF source 134. RF source 134 is coupled to electrode 118 via impedance matching circuit 136. RF source 134 is capable of providing RF power to electrode 118 at one or more frequencies simultaneously. For example, RF source 134 provides RF power to the electrode at a frequency of approximately 13.56 MHz and a frequency of approximately 40 MHz. To this end, RF source 134 includes frequency generators 138A, 138B for each frequency. Although two frequency generators 138A, 138B are shown, RF source 134 may include any number of frequency generators for each frequency used. The characteristic impedance of RF source 134 is approximately 50 ohms.

[0023] Impedance matching circuit 136 is capable of striking and maintaining a plasma in process volume 120. Impedance matching circuit 136 combines RF signals of various frequencies from RF source 134. Impedance matching circuit 136 sends the combined RF signal to electrode 118 embedded in electrostatic chuck 115. The combined RF signal is sent to the process gas in process volume 120 to generate a capacitively coupled plasma therein. Chamber body 102 is coupled to ground and provides an RF return path to facilitate the generation of the capacitively coupled plasma.

[0024] In one embodiment, the RF power provided to electrode 118 is between approximately 5 kW and approximately 15 kW, such as between approximately 8 kW and approximately 13 kW, for example approximately 10 kW. The RF current provided to electrode 118 is between approximately 120 amperes and approximately 80 amperes, such as approximately 110 amperes. The high RF current is achieved through a relatively low resistance of impedance matching circuit 136, which is between approximately 0.2 ohms and approximately 0.4 ohms. The voltage delivered to electrode 118 is between approximately 8 kV and approximately 13 kV, such as approximately 10 kV. The impedance angle of impedance matching circuit 136 is between approximately 85 degrees and approximately 90 degrees, for example, between approximately 87 degrees and approximately 89 degrees.

[0025] Electrode 122 is a component of electrostatic chuck 115 disposed on substrate support 114. A dielectric layer (not shown) may be disposed on electrostatic chuck 115 and form surface 116 of electrostatic chuck 115. Power supply 132 is coupled to electrode 122 and provides sufficient power to electrode 122 to generate an electrostatic force to hold the substrate on surface 116 of electrostatic chuck 115. In one embodiment that may be combined with one or more of the above embodiments, power supply 132 provides direct current (DC) power to electrode 122.

[0026] The coupling capacitance of electrode 122 is between approximately 800 pF and approximately 2500 pF. In one embodiment combinable with one or more of the above embodiments, electrode 122 is made of an aluminum-containing material. In one embodiment combinable with one or more of the above embodiments, electrode 122 is disposed between electrode 118 and surface 116 of electrostatic chuck 115.

[0027] When plasma is generated in process volume 120, RF current enters electrode 122 and flows toward power supply 132 (e.g., RF leakage). The RF current entering and flowing through power supply 132 can damage power supply 132, which can result in power loss of the electrode and loss of the clamping force applied to the substrate disposed thereon. To prevent damage to power supply 132, filter circuit 130 is placed between power supply 132 and electrode 122.

[0028] Filter circuit 130 (such as an RF filter) substantially prevents RF current from flowing toward power supply 132. Thus, filter circuit 130 substantially reduces the occurrence of damage to power supply 132 by redirecting the RF current (e.g., to ground). The input impedance of filter circuit 130 is high enough relative to ground such that a minimal amount of current is transferred from the substrate and the plasma. However, the impedance of filter circuit 130 is low enough to substantially prevent current from flowing toward power supply 132.

[0029] Controller 124 is coupled to process chamber 100 to control various aspects of the processes performed therein. For example, controller 124 controls the flow rate of process gas from gas delivery system 126 to process volume 120. Controller 124 can also control aspects of loading and unloading substrates from process chamber 100. Additionally, controller 124 can control aspects of impedance matching circuit 136 and filter circuit 130, such as the capacitance of variable capacitors.

[0030] Figure 2A is a schematic representative diagram of filter circuit 200 according to one embodiment. Filter circuit 200 can correspond to filter circuit 130 described above with respect to Figure 1 Filter circuit 200 includes a first inductor 202 coupled to an electrode (such as electrode 122 shown in Figure 1 ). A second inductor 206 is disposed in series with first inductor 202. A third inductor 210 is disposed in series with first inductor 202 and second inductor 206. A resistor 214 is disposed in series with first inductor 202, second inductor 206, and third inductor 210. Resistor 214 is coupled to a power source, such as Figure 1 power supply 132 shown in

[0031] The first capacitor 204 is arranged in parallel with the second inductor 206. The first capacitor 204 and the second inductor 206 form an L-C resonant circuit. The first ground path includes a second capacitor 208 which is coupled to the filter circuit 200 between the second inductor 206 and the third inductor 210 and is coupled to ground. The second ground path includes a third capacitor 212 which is coupled to the filter circuit 200 between the third inductor 210 and the resistor 214 and is coupled to ground. The second capacitor 208 and the third capacitor 212 are shunt capacitors coupled to ground.

[0032] A first portion 231 of the filter circuit includes a first inductor 202, a second inductor 206, and a first capacitor 204. The first portion 231 is the inductive portion of the filter circuit 200. Most of the RF current entering the filter circuit 200 at 13.56 MHz is removed by the first inductor 202. Similarly, most of the RF current at 40 MHz is removed by the L-C resonant circuit including the second inductor 206 and the first capacitor 204.

[0033] A second portion 233 of the filter circuit 200 is a low-pass filter and includes the second capacitor 208, the third inductor 210, and the third capacitor 212. The resistor 214 is an optional current-limiting resistor between the second portion 233 and the power supply. The second portion 233 removes any remaining RF current from the filter circuit 200 to prevent RF current leakage into the power supply connected to the resistor 214.

[0034] The values of the components of the filter circuit 200 (e.g., the first inductor 202, the second inductor 206, the third inductor 210, the first capacitor 204, the second capacitor 208, the third capacitor 212, and the resistor 214) can be tuned based on one or more frequencies of the RF current flowing therethrough. For example, in one embodiment which can be combined with one or more of the above embodiments, the first inductor 202 has an inductance ranging from about 14 μH to about 25 μH, such as about 20 μH, the third inductor 210 has an inductance ranging from about 8 μH to about 13 μH, such as about 10 μH, the second capacitor 208 and the third capacitor 212 have an inductance ranging from about 800 pF to about 15000 pF, for example about 1000 pF, and the resistor has a resistance ranging from about 1 Ω to about 5 Ω, such as about 2 Ω.

[0035] The L-C resonant circuit (including the first capacitor 204 and the second inductor 206) may have a resonant frequency of 40 MHz. The values of the components in the first part 231 (e.g., the first inductor 202, the second inductor 206, and the first capacitor 204) may be based on an input frequency of 13.56 MHz. That is, the first part 231 may be designed to remove RF current at a frequency of 13.56 MHz.

[0036] Advantageously, Figure 2A the filter circuit 200 shown in substantially reduces the Figure 1 RF current flowing from the electrode 122 shown in to the power supply 132. Accordingly, the filter circuit 200 substantially reduces the degree and incidence of damaging the power supply.

[0037] Figure 2B is a schematic representation of a filter circuit 270 according to an embodiment. The filter circuit 270 may correspond to the filter circuit 130 described above with reference to Figure 1 That is, the filter circuit 270 may be an alternative design to the filter circuit 200 described above with reference to Figure 2A being described.

[0038] The filter circuit 270 includes a first part 260 and a second part 262. The first part 260 includes a first inductor group 230 and a second inductor group 232 connected in series. The second part 262 includes a capacitor group 234, a third inductor group 236, and a shunt capacitor 254. The capacitor group 234 and the shunt capacitor 254 are in parallel. As shown, the first inductor group 230 includes four inductors 240a, 240b, 240c, and 240d connected in parallel. The second inductor group 232 includes four inductors 242a, 242b, 242c, and 242d connected in parallel. The first part 260 of the filter circuit 270 has a combined inductance of 20 μH.

[0039] As shown, the second part 262 of the filter circuit 270 is a low-pass filter. The capacitor group 234 includes four capacitors 246, 248, 250, and 252. The third inductor group includes three inductors 244a, 244b, and 244c connected in parallel. The capacitance of each of the capacitors 246, 248, 250, 252, and 254 is 1000 pF. The inductance of the third inductor group 236 is approximately 10 μH. The values of the components of the filter circuit 270 may be tuned based on one or more input frequencies to be removed by the filter circuit 270.

[0040] Figure 3FIG. 0 is a schematic representative view of an impedance matching circuit 300 according to one embodiment. The impedance matching circuit 300 includes a first variable capacitor 306 and an inductor 308 in series. A second variable capacitor 304 is coupled to ground and to the impedance matching circuit 300 upstream of the first variable capacitor 306. The impedance matching circuit 300 provides an input impedance of a plasma formed in a process chamber, such as the process chamber 100 described above with respect to Figure 1 as described.

[0041] Figure 4 FIG. 6 is a plan view of a cluster tool apparatus 400 according to one embodiment described herein. The apparatus 400 includes a plurality of process chambers 402, 404, 406, and 408, a transfer chamber 420, and load lock chambers 410 and 412. Each of the process chambers 402, 404, 406, and 408 is coupled to the transfer chamber 420. Although four process chambers 402, 404, 406, and 408 are shown in Figure 4 FIG. 8, any number of process chambers can be coupled to the transfer chamber 420.

[0042] In one embodiment that can be combined with one or more of the above embodiments, the process chamber 402 is arranged adjacent to the process chamber 408. In one embodiment, the process chamber 404 is arranged adjacent to the process chamber 402. In one embodiment that can be combined with one or more of the above embodiments, the process chamber 406 is arranged adjacent to the process chamber 404. In one embodiment that can be combined with one or more of the above embodiments, each of the process chambers 402, 404, 406, and 408 corresponds to Figure 1 the process chamber 100 illustrated in

[0043] The transfer chamber 420 enables transfer of substrates between the load lock chambers 410, 412 and the process chambers 402, 404, 406, and 408. A transfer robot 414 is disposed in the transfer chamber 420. The transfer robot 414 can be a single blade robot or a dual blade robot. The transfer robot 414 has a substrate transfer blade 416 attached to the distal end of an extendable arm. The blade 416 is used to support and carry individual substrates between the process chambers 402, 404, 406, and 408. The transfer chamber 420 is maintained in a vacuum or reduced oxygen environment.

[0044] A controller 430 is coupled to the apparatus 400. The controller 430 includes a central processing unit (CPU) (not shown). The controller 430 can be in any form of a general computer processor that can be used to control various process chambers and sub - processors. The controller 430 can be coupled to individual or shared controllers of the process chambers 402, 404, 406, and 408. The controller 430 can control the movement of the transfer robot 414 for transferring substrates within the apparatus 400.

[0045] In one embodiment that can be combined with one or more of the above embodiments, adjacent process chambers (e.g., process chambers 402 and 408) have a shared gas delivery system, RF source, controller, and / or vacuum system. These shared systems increase the throughput of the processes performed in the process chambers and the consistency of the deposited films. The shared systems also reduce the costs associated with the processes.

[0046] Benefits of the present disclosure include filter circuits to reduce the amount of RF current (e.g., RF leakage) that propagates to and damages the DC power supply. The filter circuits enable the RF current to be directed away from the DC power supply and back to the RF source. The filter circuits also prevent power loss to the clamping electrodes and loss of the clamping force applied to the substrate.

[0047] Although the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure can be designed without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the appended claims.

Claims

1. An apparatus for applying radio frequency power, comprising: A chamber body and a cover, the chamber body and the cover defining a process volume in the chamber body and the cover; A substrate support disposed in the process volume; A first electrode embedded in the substrate support; A radio frequency (RF) source coupled to the first electrode; An impedance matching circuit disposed between the RF source and the first electrode; A second electrode embedded in the substrate support; A power source coupled to the second electrode; And An electrode filter disposed between the second electrode and the power source and coupled to the second electrode and the power source, wherein the electrode filter includes: A first inductor bank coupled to the second electrode, the first inductor bank including a first plurality of inductors in parallel; A second inductor bank in series with the first inductor bank, the second inductor bank including a second plurality of inductors in parallel; A third inductor bank in series with the first inductor bank and the second inductor bank, the third inductor bank including a third plurality of inductors in parallel, wherein the third inductor bank is coupled to the power source; A first ground path coupled to the electrode filter between the second inductor bank and the third inductor bank, the first ground path including a capacitor bank; and A second ground path coupled to the electrode filter between the third inductor bank and the power source, the second ground path including a shunt capacitor.

2. The apparatus according to claim 1, wherein the second electrode comprises a conductive mesh.

3. The apparatus according to claim 1, wherein the impedance matching circuit comprises: A first capacitor; An inductor in series with the first capacitor and coupled to the first electrode; And A ground path upstream of the first capacitor, the ground path including a second capacitor.

4. The apparatus according to claim 3, wherein the first capacitor and the second capacitor are variable capacitors.

5. The apparatus according to claim 1, further comprising: A gas distribution plate coupled to the chamber body and disposed relative to the substrate support.

6. The apparatus according to claim 5, wherein the second electrode is disposed between the first electrode and a surface of the substrate support facing the gas distribution plate.

7. An apparatus for applying radio frequency power, comprising: A chamber body and a cover, the chamber body and the cover defining a process volume in the chamber body and the cover; A gas distribution plate disposed in the process volume and coupled to the chamber body; A substrate support disposed in the process volume; A first electrode embedded in the substrate support; A power source coupled to the first electrode; And An electrode filter disposed between the first electrode and the power source, the electrode filter including: A first inductor bank coupled to the first electrode, the first inductor bank including a first plurality of inductors in parallel; A second inductor bank in series with the first inductor bank, the second inductor bank including a second plurality of inductors in parallel; A third inductor bank in series with the first inductor bank and the second inductor bank, the third inductor bank including a third plurality of inductors in parallel, wherein the third inductor bank is coupled to the power source; A first ground path that is coupled to the electrode filter between the second inductor bank and the third inductor bank, the first ground path including a capacitor bank; and A second ground path that is coupled to the electrode filter between the third inductor bank and the power source, the second ground path including a shunt capacitor.

8. The device according to claim 7, wherein the first electrode comprises a conductive mesh.

9. The device according to claim 7, a second electrode, the second electrode being embedded in the substrate support; a radio frequency (RF) source, the radio frequency (RF) source being coupled to the second electrode; and an impedance matching circuit, the impedance matching circuit being disposed between the RF source and the second electrode.

10. The device according to claim 9, wherein the first electrode is disposed between the second electrode and the surface of the substrate support facing the gas distribution plate.

11. The device according to claim 9, wherein the impedance matching circuit comprises: A first capacitor; An inductor that is in series with the first capacitor; And A ground path that is upstream of the first capacitor, the ground path including a second capacitor.

12. The device according to claim 11, wherein the first capacitor and the second capacitor are variable capacitors.

13. A device for applying radio frequency power, comprising: A chamber body and a lid that define a process volume in the chamber body and the lid; A gas distribution plate that is disposed in the process volume and positioned adjacent to the lid; A substrate support that is disposed in the process volume; A first electrode that is embedded in the substrate support; A second electrode that is embedded in the substrate support between the first electrode and the surface of the substrate support facing the lid; A radio frequency (RF) source that is coupled to the first electrode; An impedance matching circuit that is disposed between the RF source and the first electrode; A power source that is coupled to the second electrode; And An electrode filter that is disposed between the second electrode and the power source, the electrode filter including: A first inductor bank that is coupled to the second electrode, the first inductor bank including a first plurality of inductors in parallel; A second inductor bank that is in series with the first inductor bank, the second inductor bank including a second plurality of inductors in parallel; A third inductor bank that is in series with the first inductor bank and the second inductor bank, the third inductor bank including a third plurality of inductors in parallel, wherein the third inductor bank is coupled to the power source; A first ground path that is coupled to the electrode filter between the second inductor bank and the third inductor bank, the first ground path including a capacitor bank; and A second ground path that is coupled to the electrode filter between the third inductor bank and the power source, the second ground path including a shunt capacitor.

14. The device according to claim 13, wherein the second electrode comprises a conductive mesh.

15. The device according to claim 14, wherein the conductive mesh is made of an aluminum-containing material.

16. The device according to claim 13, wherein the second electrode generates an electrostatic force on the surface of the substrate support.

17. The device according to claim 13, wherein the impedance matching circuit comprises: A first capacitor; An inductor that is in series with the first capacitor; And A ground path that is upstream of the first capacitor, the ground path including a second capacitor.

18. The device according to claim 17, wherein the first capacitor and the second capacitor are variable capacitors.

19. The device according to claim 13, wherein each of the first plurality of inductors and the second plurality of inductors comprises four inductors.

20. The device according to claim 13, wherein the third plurality of inductors comprises three inductors.

Images