Heated pedestal with low-impedance RF rod

Abstract

This specification provides embodiments of substrate supports for use in process chambers. In some embodiments, a substrate support for a process chamber includes a pedestal having a support surface for supporting a substrate and having one or more heating elements and RF electrodes disposed inside; a hollow shaft coupled to the lower surface of the pedestal; and an RF rod extending through the hollow shaft and having an upper end coupled to the RF electrodes, wherein the upper end of the RF rod has at least one of (a) a cross-sectional width wider than the lower part of the RF rod or (b) one or more slots.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to substrate processing equipment.

Background Art

[0002] In the manufacture of integrated circuits and other electronic devices, plasma process chambers are often used for the deposition or etching of various material layers. A plasma process chamber generally includes a heating pedestal for supporting a substrate during processing and controlling the temperature of the substrate during processing. During the life of a plasma process chamber, the heated pedestal may be modified to extend the chamber life or replaced to accommodate different processes. However, a modified pedestal or a different pedestal may cause an impedance mismatch where the input impedance of the electrical load does not match the output impedance of the signal source, resulting in signal reflections or inefficient power transmission that can cause process shifts.

[0003] Therefore, the inventors herein provide embodiments of an improved substrate support for use in a plasma process chamber.

Summary of the Invention

[0004] Embodiments of a substrate support for use in a process chamber are provided herein. In some embodiments, a substrate support for a process chamber has a support surface for supporting a substrate, a pedestal having one or more heating elements disposed therein and an RF electrode disposed therein, a hollow shaft coupled to the lower surface of the pedestal, and an RF rod having an upper portion that extends through the hollow shaft and has an upper end coupled to the RF electrode, wherein the upper end of the RF rod has (a) a cross-sectional width wider than the lower portion of the RF rod or (b) at least one of one or more slots.

[0005] In some embodiments, the substrate support for the process chamber includes a pedestal having a support surface for supporting a substrate and having one or more heating elements disposed inside and an RF electrode disposed inside; a hollow shaft coupled to the lower surface of the pedestal; and an RF rod extending through the hollow shaft and having an upper end coupled to the RF electrode, wherein the RF transmission path of the RF rod, including the sum of the lengths of all edges arranged along the upper end, is longer than the sum of the lengths of the outer circumference of the upper end of the RF rod, and the upper end of the RF rod has at least one of (a) a cross-sectional width wider than the lower part of the RF rod or (b) one or more slots.

[0006] In some embodiments, the process chamber includes a chamber body defining an internal volume; a substrate support disposed within the internal volume, having a support surface for supporting a substrate, and including a pedestal in which one or more heating elements and an RF electrode are disposed inside; a hollow shaft coupled to the lower surface of the pedestal; and an RF rod extending through the hollow shaft and having an upper part including an upper end coupled to the RF electrode, wherein the upper end of the RF rod has at least one of (a) a cross-sectional width wider than the lower part of the RF rod or (b) one or more slots.

[0007] Other and further embodiments of this disclosure are described below.

[0008] The embodiments of this disclosure, which are briefly summarized above and discussed in more detail below, can be understood by referring to the exemplary embodiments of this disclosure shown in the accompanying drawings. However, the accompanying drawings show only typical embodiments of this disclosure and should not be considered limiting in scope, as this disclosure may allow for other equally valid embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic side view of a process chamber according to at least some embodiments of the present disclosure. [Figure 2]This is an isometric view of a substrate support according to at least some embodiments of the present disclosure. [Figure 3] This is a schematic side cross-sectional view of a portion of a substrate support according to at least some embodiments of the present disclosure. [Figure 4A] This is the cross-sectional shape of an RF rod according to at least some embodiments of the present disclosure. [Figure 4B] This is the cross-sectional shape of an RF rod according to at least some embodiments of the present disclosure. [Figure 4C] This is the cross-sectional shape of an RF rod according to at least some embodiments of the present disclosure. [Figure 4D] This is the cross-sectional shape of an RF rod according to at least some embodiments of the present disclosure. [Figure 4E] This is the cross-sectional shape of an RF rod according to at least some embodiments of the present disclosure. [Figure 4F] This is the cross-sectional shape of an RF rod according to at least some embodiments of the present disclosure. [Figure 4G] This is the cross-sectional shape of an RF rod according to at least some embodiments of the present disclosure. [Figure 5] This is an isometric view of the top of an RF rod according to at least some embodiments of the present disclosure. [Figure 6] This is an isometric view of the top of an RF rod according to at least some embodiments of the present disclosure. [Figure 7] This is an isometric view of the top of an RF rod according to at least some embodiments of the present disclosure. [Figure 8] This is an isometric view of the top of an RF rod according to at least some embodiments of the present disclosure.

[0010] For ease of understanding, the same reference numerals are used to indicate identical elements common to the drawings, where possible. The drawings are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be incorporated into other embodiments for the benefit of the latter without further detail. [Modes for carrying out the invention]

[0011] This specification provides embodiments of a substrate support having an RF rod with reduced impedance. The RF rod is configured to supply RF power from an RF power supply to RF electrodes placed on the substrate support. Impedance mismatch occurs when the input impedance of an electrical load does not match the output impedance of a signal source, such as an RF power supply, which can lead to reduced power efficiency and a decrease in deposition rate. However, increasing the impedance of an electrical load is easier to achieve than reducing the impedance of an electrical loss. Therefore, the inventors have found that reducing the impedance of the RF rod to a value less than or equal to the output impedance is advantageous for impedance matching. The substrate support described herein includes an RF rod having an upper end with features such as one or more slots to advantageously increase the RF transmission path and reduce the impedance of the RF rod.

[0012] RF energy is typically transmitted along the edges of a surface. For example, in a conventional RF rod with a flat top end, the RF transmission path extends along the circumference or outer edge of the RF rod. An top end with features (e.g., one or more slots arranged along the top end) advantageously increases the effective length of the RF transmission path, improves RF transmission, and reduces impedance. In some embodiments, an adjustable impedance device is coupled to the RF rod and configured to adjust the impedance of the substrate support to match the output impedance before the substrate support is placed in the process chamber.

[0013] Figure 1 is a schematic side cross-sectional view of a plasma processing chamber according to at least some embodiments of the present disclosure. The plasma process chamber, or chamber 100, generally includes a chamber body 102 that defines an internal volume 103. A substrate support 108 is positioned within the internal volume 103 and supports a substrate 110 placed thereon. The chamber 100 is generally configured to deposit one or more films on the substrate 110 or to etch one or more films from the substrate 110. The chamber 100 further includes a gas distribution assembly 104 that uniformly distributes gas into a process volume 106 of the internal volume 103, which is generally defined by the region between the gas distribution assembly 104 and the substrate support 108.

[0014] The substrate support 108 includes a pedestal 132 coupled to a hollow shaft 114. The pedestal 132 is movably positioned within the internal volume 103 via the hollow shaft 114 extending through the chamber body 102, which is connected to a drive system 105 and bellows, thereby enabling the pedestal 132 to be raised and / or rotated. The gas distribution assembly 104 includes a gas inlet passage 116 that supplies gas from the gas flow controller 120 to the gas distribution manifold 118. The gas distribution manifold 118 includes a number of holes 152 or nozzles through which the gas mixture is injected into the process volume 106 during processing.

[0015] High-frequency RF power supplies, such as RF power supply 126, and low-frequency RF power supplies, such as RF power supply 127, supply electromagnetic energy via a matching circuit 129 to power a gas distribution manifold 118, which acts as an RF drive electrode, thereby facilitating plasma generation in the process volume 106 between the gas distribution manifold 118 and the pedestal 132. The pedestal 132 includes an RF electrode 112, which is electrically grounded via an RF rod 122, thereby generating an electric field between the powered gas distribution manifold 118 and the RF electrode 112 within the chamber 100. The RF rod 122 may be made of copper, nickel, or the like. In some embodiments, the RF electrode 112 includes a conductive mesh, such as a tungsten or molybdenum-containing mesh, placed within a dielectric material used to form the pedestal 132. The pedestal 132 may include ceramic materials such as aluminum nitride (AlN), silicon nitride (SiN), or silicon carbide (SiC).

[0016] A ceramic ring 123 is positioned beneath the gas distribution manifold 118. Optionally, a tuning ring 124 is positioned between the ceramic ring 123 and the isolator 125, thereby electrically isolating the tuning ring 124 from the chamber body 102. The tuning ring 124 is typically made from a conductive material such as aluminum, titanium, or copper. As shown in Figure 1, the tuning ring 124 is positioned concentrically around the pedestal 132 and the substrate 110 during processing of the substrate 110. The tuning ring 124 may be electrically coupled to an RF tuner 135 which includes a variable capacitor 128, such as a variable vacuum capacitor terminated to ground via an inductor L1. The RF tuner 135 also includes a second inductor L2 electrically coupled in parallel to the variable capacitor 128, providing a path for low-frequency RF to ground. The RF tuner 135 also includes sensors 130, such as a voltage / current (V / I) sensor, which is positioned between the tuning ring 124 and the variable capacitor 128 and used to control the flow of current through the tuning ring 124 and the variable capacitor 128.

[0017] In some embodiments, the RF rod 122 is coupled to an impedance adjustment device 145 having at least one of a variable inductor or a variable resistor (described in more detail with respect to FIG. 3) configured to vary the impedance of the substrate support 108. The impedance of the substrate support 108 may include other resistances such as the impedance of the RF rod 122, the impedance of the junction between the RF rod 122 and the RF electrode 112, and the equivalent series resistance of the components along the path between the RF source and the substrate support 108. The impedance adjustment device 145 can be advantageously used to adjust the substrate support 108 to a target impedance value. In some embodiments, the target impedance of the substrate support 108 after adjustment via the impedance adjustment device 145 is less than about 0.4 ohms. In some embodiments, the target impedance of the substrate support 108 after adjustment via the impedance adjustment device 145 is about 0.2 ohms to 0.4 ohms. The impedance of a conventional RF rod may be an impedance of about 0.17 ohms or more. Because the RF rod 122 has a low impedance, compared to prior art devices, the RF power loss is advantageously reduced and / or the adjustment for matching the impedance of the substrate support 108 to the impedance of the RF source is facilitated. For example, in some embodiments, the impedance of the RF rod 122 is less than about 0.17 ohms. In some embodiments, the impedance of the RF rod 122 is less than about 0.06 ohms. In some embodiments, the impedance adjustment device 145 is configured to vary the impedance of the substrate support 108 by about 0.05 to about 0.1 ohms.

[0018] One or more heating elements 150 are disposed within the pedestal 132 and are used to control the temperature profile across the substrate 110. In some embodiments, one or more heating elements 150 are disposed beneath the RF electrode 112. The one or more heating elements 150 generally provide resistive heating to the substrate 110 and may be composed of any practicable material, such as a conductive metal wire (e.g., a high melting point metal wire), a patterned metal layer (e.g., a molybdenum, tungsten, or other high melting point metal layer), or other similar conductive structures. The heating element 150 is connected to one or more conductive rods 155 that can extend along the length of the hollow shaft 114 of the pedestal 132. In some embodiments, the conductive rods 155 are disposed substantially parallel to the RF rods 122.

[0019] The conductive rod 155 couples the heating element 150 to a heating power supply 165 via one or more RF filters 160. The RF rod 122 and the conductive rod 155 are generally solid conductive elements (e.g., medium diameter single wires, unstranded wires) formed from a conductive material such as copper, nickel, gold, coated aluminum, high melting point metals, etc. The RF filter 160 is generally either a low-pass filter or a band-stop filter configured to prevent RF energy from reaching the heating power supply 165. In some embodiments, the heating power supply 165 supplies non-RF alternating current (AC) power to the heating element 150. For example, the heating power supply 165 can supply three-phase AC power at a frequency of about 60 hertz.

[0020] In some embodiments, including the RF filter 160 in the heating assembly can provide a relatively large impedance path to ground and minimize the amount of RF leakage to the heating element 150. The RF filter 160 may be inserted between the heating element 150 and the corresponding AC power supply to attenuate RF energy and suppress RF leakage current. In some configurations, the ground impedance of the RF electrode 112 is substantially smaller than the ground impedance of the heating element 150.

[0021] The system controller 134 controls the functions of various components, including RF power supplies 126 and 127, the drive system 105, the variable capacitor 128, and the heating power supply 165. The system controller 134 executes system control software stored in memory 138. The system controller 134 comprises one or more integrated circuits (ICs) and / or some or all of other circuit components. The system controller 134 may optionally include a central processing unit (CPU) (not shown), memory (not shown), and support circuits (or I / O) (not shown). The CPU may be one of any form of computer processor used to control various system functions, support hardware, and monitor processes controlled by and within Chamber 100. The memory is coupled to the CPU and may be one or more readily available memories, such as random access memory (RAM), read-only memory (ROM), floppy disks, hard disks, or any other form of local or remote digital storage. Software instructions (or computer instructions) and data may be coded and stored in memory to instruct the CPU. Software instructions can include programs that determine which tasks are executed at what moment. Support circuits also connect to the CPU to support the processor in a conventional way. Support circuits can include caches, power supplies, clock circuits, timing circuits, input / output circuits, and subsystems.

[0022] During use, an RF path is established between the gas distribution manifold 118, which is powered via the plasma, and the RF electrode 112. Furthermore, by changing the capacitance of the variable capacitor 128, the impedance of the RF path through the RF electrode 112 is changed, which in turn causes a change in the RF electric field coupled to the RF electrode 112 and a change in the RF return current passing through the RF electrode 112 and the RF rod 122. Thus, the plasma in the process volume 106 can be modulated across the entire surface of the substrate 110 during plasma processing, thereby improving processing uniformity.

[0023] Furthermore, in some embodiments, an additional RF path is established between the powered gas distribution manifold 118 and the tuning ring 124. Additionally, by changing the capacitance of the variable capacitor 128, the impedance of the RF path through the tuning ring 124 is changed, thereby causing a change in the RF electric field coupled to the tuning ring 124. For example, by changing the total capacitance of the variable capacitor 128, the maximum current and corresponding minimum impedance of the tuning ring 124 can be achieved. Thus, by using the additional RF path, the plasma within the process volume 106 can also be modulated across the entire surface of the substrate 110.

[0024] Figure 2 shows an isometric view of a substrate support 108 according to at least some embodiments of the present disclosure. The RF rod 122 extends through the hollow shaft 114 of the substrate support 108 and is coupled to the pedestal 132 of the substrate support 108. In some embodiments, the RF rod 122 is located radially outward from the center 210 of the pedestal 132. In some embodiments, the RF rod 122 includes one or more slits 290 in the form of gaps to facilitate the reduction of stress on the RF rod 122 during thermal cycling. In some embodiments, one or more slits 290 are located near the lower end of the RF rod 122. In some embodiments, a spacer plate 208 is placed inside the hollow shaft 114 to position the RF rod 122 within the hollow shaft. The spacer plate 208 may include one or more openings 212 for accommodating the RF rod 122 and the conductive rod 155 and maintaining the spacing between them. In some embodiments, the spacer plate 208 is placed inside the hollow shaft 114 at the lower end 218 of the RF rod 122. Spacer plate 208 is generally made of insulating material.

[0025] The hollow shaft 114 may be coupled to a lower block 204 made of a metallic material, such as stainless steel. In some embodiments, a feedthrough 222 is located within the lower block 204 to provide an electrical feedthrough for one or more conductive rods 155. In some embodiments, the feedthrough 222 is configured to facilitate a path for the RF rod 122 to ground. In some embodiments, the lower end 218 of the RF rod 122 is coupled to a ceramic insulator 220 located within the lower block 204. The ceramic insulator 220 can separate the spacer plate 208 from the feedthrough 222 and the lower block 204 and can be configured for higher temperature applications.

[0026] Figure 3 shows a schematic side cross-sectional view of a portion of the substrate support 108 according to at least some embodiments of the present disclosure. The inventors have found that the impedance of the substrate support 108 can be reduced by plating the RF rod 122 or by brazing the RF rod 122 to the RF electrode 112. For example, the RF rod 122 may be plated with nickel, gold, or silver. In some embodiments, the thickness of the plating is about 30 to about 50 micrometers. In some embodiments, the RF rod 122 is brazed to the RF electrode 112 via a metal 310. In some embodiments, the metal 310 is made of copper, gold, silver, or nickel.

[0027] In some embodiments, an RF electrode 112 formed within the pedestal 132 is electrically coupled to an impedance adjustment device 145 via an RF rod 122. The impedance adjustment device 145 is located within a hollow shaft 114. In some embodiments, the impedance adjustment device 145 is located within an internal volume 103. In some embodiments, the impedance adjustment device 145 includes at least one of a variable inductor 308 or a variable resistor 306. The impedance adjustment device 145 can be configured to adjust the substrate support 108 to a desired impedance value before being placed in the chamber 100. The impedance adjustment device 145 typically does not adjust the impedance of the substrate support 108 during processing of the substrate 110. In other words, the impedance adjustment device 145 does not perform adjustment at init.

[0028] Figures 4A to 4G show various cross-sectional shapes of the RF rod 122 according to at least some embodiments of the present disclosure. The inventors have found that the impedance of the substrate support 108 can be reduced by increasing the cross-sectional area of ​​the RF rod 122. In some embodiments, the RF rod 122 has a circular cross-sectional shape, as shown in Figure 4A. In some embodiments, the RF rod 122 has a non-circular cross-sectional shape. For example, Figure 4B shows an RF rod 122 having a star-shaped cross-section. Figure 4C shows an RF rod 122 having a triangular cross-section. Figure 4D shows an RF rod 122 having a square cross-section. In some embodiments, the RF rod 122 has a polygonal cross-sectional shape, for example, the RF rod 122 shown in Figures 4C and 4D. In other examples, the RF rod 122 may have a hexagonal cross-sectional shape, as shown in Figure 4E, or an octagonal cross-sectional shape, as shown in Figure 4G. In some embodiments, as shown in Figure 4F, the RF rod 122 may have a square shape with recessed features 420 at the four corners of the RF rod 122. In some embodiments, the RF rod 122 has a circular shape with a diameter of approximately 0.10 inches to approximately 0.14 inches. In some embodiments, the diameter of the RF rod 122 is approximately 0.11 inches to approximately 0.13 inches.

[0029] Figure 5 shows an isometric view of the upper part 510 of an RF rod according to at least some embodiments of the present disclosure. The RF rod 122 is coupled to an RF electrode 112 via an upper end 504 of the RF rod 122. The upper end is a discontinuous surface having features such as one or more slots 508 configured to increase the RF transmission path of the RF rod 122. For example, the RF transmission path of the RF rod 122 may include the total straight length of all edges arranged along the upper end 504. The RF transmission path of the RF rod 122 having features such as one or more slots 508 is generally longer than the total length of the outer circumference of the upper end 504 of the RF rod 122, advantageously reducing the impedance of the RF rod 122.

[0030] For example, in the RF rod 122 shown in Figure 5, the RF rod 122 has a radius R1 and therefore has an outer circumference or circle of 2 × R1 × π. One or more slots 508 arranged along the upper end 504 divide the upper end 504 into four parts 520A to 520D. Each of the four parts 520A to 520D defines a linear edge along the upper end 504 defined by two radial edges, each radial edge having a length E1 and connected to a curved outer edge having a length E2. Thus, for each of the four parts 520A to 520D, the straight length of all edges arranged along the upper end 504 is length E1 + length E1 + length E2, i.e., L1. Therefore, the RF transmission path of the RF rod 122 shown in Figure 5 is four times L1.

[0031] In some embodiments, the depth D1 of one or more slots 508 is greater than the width W1 of the upper end 504, or the diameter in the case of a circular RF rod. In some embodiments, one or more slots 508 have a width W2 of about 0.01 inches or more to reduce or prevent arc discharge. In some embodiments, the depth D1 is greater than about 0.01 inches. In some embodiments, the depth D1 is about 0.01 to about 0.02 inches. One or more slots 508 are also configured such that the upper end 504 has a surface area sufficient to provide a good bond with the RF electrode 112, for example, a good brazed bond via metal 310. In some embodiments, one or more slots 508 include a plurality of slots extending from the center 502 of the upper end 504 to the outer edge 514 of the upper end 504. In some embodiments, as shown in Figure 5, one or more slots 508 consist of two slots intersecting at the center 502 of the upper end 504.

[0032] Figure 6 shows an isometric view of the upper part 510 of the RF rod 122 according to at least some embodiments of the present disclosure. In some embodiments, as shown in Figure 6, one or more slots 508 consist of four slots that intersect at the center 502 of the upper end 504, so that the upper end 504 is divided into eight parts. Thus, the RF rod 122 of Figure 6 has a longer RF transmission path than the RF transmission path of the RF rod 122 shown in Figure 5.

[0033] In some embodiments, the RF rod 122 includes a lower section 610 extending from an upper section 510. The inventors have found that the impedance of the RF rod 122 can be reduced by increasing the cross-sectional area of ​​the upper section 510 of the RF rod 122. Therefore, in some embodiments, the cross-sectional width of the upper section 510, or the diameter in the case of a circular RF rod, is greater than the width of the lower section 610, or the diameter in the case of a circular RF rod. One or more slots 508 are generally located in the upper section 510. In some embodiments, the upper section 510 includes a tapered section 608 located between the top 606 and the lower section 610. The tapered section 608 is narrower in width or diameter from the top 606 to the lower section 610.

[0034] One or more slots 508 may be arranged in any suitable pattern to increase the RF transmission paths of the RF rod 122. For example, Figure 7 shows an isometric view of the upper part 510 of the RF rod 122 according to at least some embodiments of the present disclosure. In some embodiments, one or more slots 508 include multiple slots arranged in multiple parallel columns. Figure 8 shows an isometric view of the upper part 510 of the RF rod 122 according to at least some embodiments of the present disclosure. In some embodiments, one or more slots 508 are arranged in a rectangular grid. In some embodiments, one or more slots 508 may be arranged in one or more curved or annular patterns.

[0035] While the foregoing applies to embodiments of the present disclosure, other and further embodiments of the present disclosure can be conceived without departing from the fundamental scope of the present disclosure.

Claims

1. A pedestal having a support surface for supporting a substrate, with one or more heating elements disposed inside and an RF electrode disposed inside, A hollow shaft connected to the lower surface of the pedestal, An RF rod having an upper part extending through the hollow shaft and including an upper end coupled to the RF electrode, wherein the upper end of the RF rod has at least one of (a) a cross-sectional width wider than the lower part of the RF rod or (b) one or more slots, A substrate support for a process chamber, comprising the above features.

2. The substrate support according to claim 1, wherein the RF rod is coupled to an impedance adjustment device having at least one of a variable inductor or a variable resistor.

3. The substrate support according to claim 1, wherein the upper end of the RF rod has one or more slots.

4. The substrate support according to claim 3, wherein the one or more slots include a plurality of slots extending from the center of the upper end to the outer edge of the upper end.

5. The one or more slots are arranged in multiple parallel columns, or The one or more slots are arranged in a rectangular grid, A substrate support according to claim 3, which is at least one of the two.

6. The substrate support according to claim 3, wherein the depth of one or more slots is greater than the width of the upper end.

7. The substrate support according to claim 1, wherein the cross-sectional width of the upper end of the RF rod is wider than that of the lower part of the RF rod.

8. The substrate support according to claim 7, wherein the upper part of the RF rod includes a tapered portion disposed between the upper end and the lower part.

9. The RF rod is brazed to the RF electrode with copper, gold, silver, or nickel, or The RF rod is plated with nickel, gold, or silver, A substrate support according to any one of claims 1 to 8, wherein it is at least one of the above.

10. The substrate support according to any one of claims 1 to 8, wherein the RF transmission path of the RF rod, including the total length of all edges arranged along the upper end, is longer than the total length of the outer circumference of the upper end of the RF rod.

11. The substrate support according to any one of claims 1 or 3 to 8, further comprising an impedance adjustment device disposed within the hollow shaft, wherein the impedance adjustment device includes at least one of a variable inductor or a variable resistor.

12. The substrate support according to any one of claims 1 to 8, wherein the lower end of the RF rod is bonded to a ceramic insulator.

13. The substrate support according to any one of claims 1 to 8, wherein one or more of the slots have a width of about 0.01 inches or more.

14. A chamber body that defines the internal volume, A substrate support according to any one of claims 1 to 8, disposed within the internal volume, A process chamber equipped with a process chamber.

15. The RF rod is brazed to the RF electrode with copper, gold, silver, or nickel, or The RF rod is plated with nickel, gold, or silver, The process chamber according to claim 14, which is at least one of the two.

16. The process chamber according to claim 14, wherein the RF transmission path of the RF rod is longer than the total length of the outer circumference of the upper end of the RF rod, and the RF transmission path includes the total length of all edges arranged along the upper end.

17. The process chamber according to claim 14, wherein the RF electrode includes a mesh.

18. A heating power supply coupled to one or more heating elements, A plurality of RF filters are disposed between the heating power supply and the plurality of heating elements, The process chamber according to claim 14, further comprising:

19. The process chamber according to claim 14, further comprising a spacer plate disposed within the hollow shaft at the lower end of the RF rod.

20. The process chamber according to claim 14, wherein the RF rod is positioned radially outward from the center of the pedestal.

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