Heated pedestal containing impedance-matched radio frequency (RF) rods

Abstract

Described herein are embodiments of a substrate support for a process chamber. In some embodiments, the substrate support for a process chamber includes a pedestal having a support surface for supporting a substrate, one or more heating elements disposed therein, and a radio frequency (RF) electrode disposed therein, a hollow shaft coupled to a lower surface of the pedestal, and an RF rod extending through the hollow shaft and coupled to the RF electrode, wherein the RF rod has an impedance of less than about 0.2 ohms.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to substrate processing equipment. [Background technology]

[0002] In the manufacture of integrated circuits and other electronic devices, plasma process chambers are often used to deposit or etch various material layers. Plasma process chambers typically include a heated pedestal for supporting and controlling the temperature of a substrate during processing. Over the life of a plasma process chamber, the heated pedestal may be modified to extend chamber life or replaced to accommodate a different process. However, a modified or different pedestal can cause an impedance mismatch, in which the input impedance of the electrical load does not match the output impedance of the signal source, resulting in signal reflections or inefficient power transfer, which can cause process shifts.

[0003] Accordingly, we have described herein embodiments of an improved substrate support for use in a plasma processing chamber. Summary of the Invention

[0004] Described herein are embodiments of a substrate support for a process chamber. In some embodiments, the substrate support for a process chamber includes a pedestal having a support surface for supporting a substrate, one or more heating elements disposed therein, and a radio frequency (RF) electrode disposed therein, a hollow shaft coupled to a lower surface of the pedestal, and an RF rod extending through the hollow shaft and coupled to the RF electrode, wherein the RF rod has an impedance of less than about 0.2 ohms.

[0005] In some embodiments, a substrate support for a process chamber includes a pedestal having one or more heating elements and an RF electrode disposed therein and a support surface for supporting a substrate, a hollow shaft coupled to a lower surface of the pedestal, and an RF rod extending through the hollow shaft and coupled to the RF electrode, wherein the RF rod has an impedance less than about 0.2 ohms, and the RF rod is coupled to an impedance adjustment device.

[0006] In some embodiments, the process chamber includes a chamber body defining an internal volume therein and a substrate support disposed within the internal volume, the substrate support including one or more heating elements and an RF electrode disposed therein, and a pedestal having a support surface for supporting a substrate, a hollow shaft coupled to a lower surface of the pedestal, and an RF rod extending through the hollow shaft and coupled to the RF electrode, wherein the RF rod has an impedance of less than about 0.2 ohms.

[0007] Other and additional embodiments of the present disclosure are disclosed below.

[0008] Embodiments of the present disclosure, briefly outlined above and discussed in more detail below, can be understood by reference to exemplary embodiments thereof as illustrated in the accompanying drawings. However, the accompanying drawings depict only typical embodiments of the present disclosure and, therefore, should not be considered limiting in scope, as the present disclosure may embrace other embodiments that are equally effective. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic side view of a process chamber in accordance with at least some embodiments of the present disclosure. [Figure 2] FIG. 1 is an isometric view of a substrate support according to at least some embodiments of the present disclosure. [Figure 3] 1 is a schematic cross-sectional side view of a portion of a substrate support in accordance with at least some embodiments of the present disclosure. [Figure 4A] 1A-1C illustrate various cross-sectional shapes of RF rods in accordance with at least some embodiments of the present disclosure. [Figure 4B] 1A-1C illustrate various cross-sectional shapes of RF rods in accordance with at least some embodiments of the present disclosure. [Figure 4C] 1A-1C illustrate various cross-sectional shapes of RF rods in accordance with at least some embodiments of the present disclosure. [Figure 4D] 1A-1C illustrate various cross-sectional shapes of RF rods in accordance with at least some embodiments of the present disclosure. [Figure 4E] 1A-1C illustrate various cross-sectional shapes of RF rods in accordance with at least some embodiments of the present disclosure. [Figure 4F] 1A-1C illustrate various cross-sectional shapes of RF rods in accordance with at least some embodiments of the present disclosure. [Figure 4G] 1A-1C illustrate various cross-sectional shapes of RF rods in accordance with at least some embodiments of the present disclosure. [Figure 5A] 1A-1C illustrate various side profiles of an RF rod in accordance with at least some embodiments of the present disclosure. [Figure 5B] 1A-1C illustrate various side profiles of an RF rod in accordance with at least some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] To facilitate understanding, the same reference numerals have been used, where possible, to designate identical elements common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without additional description.

[0011] Described herein are embodiments of a substrate support for a process chamber. The inventors have recognized that a substrate support having a higher impedance than a threshold substrate support can lead to a low deposition rate during processing. To facilitate matching the impedance of the threshold substrate support, the substrate support typically includes a pedestal coupled to a radio frequency (RF) rod having a low impedance. In some embodiments, the substrate support includes a tunable impedance device coupled to the RF rod, the tunable impedance device configured to adjust the impedance of the substrate support to match the threshold substrate support prior to installation in the process chamber.

[0012] 1 is a schematic cross-sectional side view of a plasma processing chamber in accordance with at least some embodiments of the present disclosure. The plasma process chamber, or chamber 100, generally includes a chamber body 102 defining an interior volume 103 therein. A substrate support 108 is disposed within the interior volume 103 for supporting a substrate 110 disposed on the substrate support 108. The chamber 100 is generally configured to deposit one or more films on or etch from the substrate 110. The chamber 100 further includes a gas distribution assembly 104 that uniformly distributes gas within a process volume 106 of the interior volume 103, generally defined by the area between the gas distribution assembly 104 and the substrate support 108.

[0013] The substrate support 108 includes a pedestal 132 coupled to a hollow shaft 114. The pedestal 132 is movably disposed within the interior volume 103 by the hollow shaft 114, which extends through the chamber body 102 and is connected to a drive system 105 and a bellows to enable the pedestal 132 to be raised, lowered, and / or rotated.

[0014] The gas distribution assembly 104 includes a gas inlet passage 116 that supplies gas from a gas flow controller 120 into a gas distribution manifold 118. The gas distribution manifold 118 includes a plurality of holes 152 or nozzles through which a gas mixture is injected into the process volume 106 during processing.

[0015] High-frequency RF power sources 126 and low-frequency RF power sources 127 provide electromagnetic energy through a matching network 129 to power the gas distribution manifold 118, which acts as an RF powered electrode, to facilitate 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 through an RF rod 122 to generate an electric field within the chamber 100 between the powered gas distribution manifold 118 and the RF electrode 112. 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, disposed within the dielectric material used to form the pedestal 132. The pedestal 132 may include a ceramic material, such as aluminum nitride (AlN), silicon nitride (SiN), or silicon carbide (SiC).

[0016] A ceramic ring 123 is disposed below the gas distribution manifold 118. Optionally, a tuning ring 124 is disposed between the ceramic ring 123 and an isolator 125, which electrically isolates the tuning ring 124 from the chamber body 102. The tuning ring 124 is typically made of a conductive material such as aluminum, titanium, or copper. As shown in FIG. 1 , the optional tuning ring 124 is concentrically disposed 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 through inductor L1. To provide a path to ground for low-frequency RF, the RF tuner 135 further includes a second inductor L2 electrically coupled in parallel with the variable capacitor 128. RF tuner 135 further includes a sensor 130, such as a voltage / current (V / I) sensor, disposed between tuning ring 124 and variable capacitor 128 for use in controlling the current through tuning ring 124 and 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 (discussed in more detail with respect to FIG. 4). The impedance adjustment device 145 may be advantageously used to tune the substrate support 108 to a target impedance value. In some embodiments, the target impedance of the RF rod 122 is less than about 0.2 ohms. In some embodiments, the impedance of the RF rod 122 is less than about 0.17 ohms. In some embodiments, the impedance adjustment device 145 is configured to change the impedance of the RF rod 122 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, the heating elements 150 are disposed below the RF electrode 112. The heating elements 150 generally provide resistive heating to the substrate 110 and may be made of any feasible material, such as conductive metal wire (e.g., refractory metal wire), patterned metal layers (e.g., molybdenum, tungsten, or other refractory metal layers), or other similar conductive structures. The heating elements 150 are connected to one or more conductive rods 155, which may 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 rods 155 couple the heating element 150 to a heating power supply 165 through one or more RF filters 160. The RF rods 122 and the conductive rods 155 are typically solid conductive elements (e.g., medium diameter solid wire, non-stranded) formed from a conductive material such as copper, nickel, gold, clad aluminum, or a refractory metal. The RF filters 160 are typically low-pass or band-stop filters configured to block 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 may supply three-phase AC power at a frequency of approximately 60 Hz.

[0020] In some embodiments, an RF filter 160 may be included in the heating assembly to provide a relatively high impedance path to ground to minimize the amount of RF leakage to the heating element 150. The RF filter 160 may be interposed between the heating element 150 and a corresponding AC source to attenuate RF energy and suppress RF leakage currents. In some configurations, the impedance of the RF electrode 112 to ground is significantly less than the impedance of the heating element 150 to ground.

[0021] System controller 134 controls the functions of various components, such as RF power supplies 126 and 127, drive system 105, variable capacitors 128 and 139, and heating power supply 165. System controller 134 executes system control software stored in memory 138. System controller 134 includes part or all of one or more integrated circuits (ICs) and / or other circuit components. In some cases, system controller 134 may include a central processing unit (CPU) (not shown), memory (not shown), and support circuitry (or I / O) (not shown). The CPU may be any form of computer processor used to control various system functions and support hardware and to monitor processes within chamber 100 that are controlled by chamber 100. Memory is coupled to the CPU and may be one or more of readily available memory, such as random access memory (RAM), read-only memory (ROM), a floppy disk, a hard disk, 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. The software instructions may include a program that determines which task to perform at any given moment. Support circuits are also connected to the CPU for supporting the processor in a conventional manner. The support circuits may include cache, power supplies, clock circuits, timing circuits, input / output circuits, subsystems, etc.

[0022] In use, an RF path is established through the plasma between the powered gas distribution manifold 118 and the RF electrode 112. Furthermore, by varying the capacitance of the variable capacitor 139, the impedance of this RF path through the RF electrode 112 is varied, which causes a change in the RF field coupled to the RF electrode 112 and a change in the RF return current through the RF electrode 112 and the RF rods 122. Thus, during plasma processing, the plasma in the process volume 106 may be tuned across the surface of the substrate 110 to improve process uniformity.

[0023] Additionally, in some embodiments, an additional RF path is established between the powered gas distribution manifold 118 and the tuning ring 124. Furthermore, by changing the capacitance of the variable capacitor 128, the impedance of this RF path through the tuning ring 124 changes, which causes a change in the RF field coupled to the tuning ring 124. For example, by changing the total capacitance of the variable capacitor 128, a maximum current and corresponding minimum impedance for the tuning ring 124 can be achieved. Thus, this additional RF path may be used to further adjust the plasma in the process volume 106 across the surface of the substrate 110.

[0024] 2 shows an isometric view of a substrate support 108 in accordance with 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 disposed 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 reducing stress on the RF rod 122 during thermal cycling. In some embodiments, the one or more slits 290 are disposed near the lower end of the RF rod 122. In some embodiments, a spacer plate 208 is disposed within the hollow shaft 114 to position the RF rod 122 within the hollow shaft 114. The spacer plate 208 may include one or more openings 212 to accommodate the RF rod 122 and the conductive rod 155 and maintain spacing between the RF rod 122 and the conductive rod 155. In some embodiments, a spacer plate 208 is disposed at the lower end 218 of the RF rod 122 within the hollow shaft 114. The spacer plate 208 is generally made of an 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 disposed 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 passage of 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 disposed within the lower block 204. The ceramic insulator 220 may separate the spacer plate 208 from the feedthrough 222 and the lower block 204 and may be configured for higher temperature applications.

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

[0027] In some embodiments, the RF electrode 112 formed in the pedestal 132 is electrically coupled to the impedance adjustment device 145 through the RF rod 122. In some embodiments, the impedance adjustment device 145 is disposed within the hollow shaft 114. In some embodiments, the impedance adjustment device 145 is disposed at least partially within the hollow shaft 114. In some embodiments, the impedance adjustment device 145 is disposed within the interior 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 may be configured to tune the substrate support 108 to a desired impedance value prior to installation in the chamber 100. The impedance adjustment device 145 generally 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 provide in situ adjustment.

[0028] 4A-5G illustrate various cross-sectional shapes of the RF rod 122 in accordance with at least some embodiments of the present disclosure. The inventors have recognized that increasing the cross-sectional area of ​​the RF rod 122 can reduce the impedance of the substrate support 108. In some embodiments, the RF rod 122 has a circular cross-sectional shape, as shown in FIG. 4A. In some embodiments, the RF rod 122 has a non-circular cross-sectional shape. For example, FIG. 4B illustrates an RF rod 122 having a star-shaped cross-sectional shape. FIG. 4C illustrates an RF rod 122 having a triangular cross-section. FIG. 4D illustrates an RF rod 122 having a square cross-sectional shape. In some embodiments, the RF rod 122 has a polygonal cross-sectional shape. For example, the RF rod 122 as shown in FIGS. 4C and 4D. In other examples, the RF rod 122 may have a hexagonal cross-sectional shape, as shown in FIG. 4E, or an octagonal cross-sectional shape, as shown in FIG. 4G. In some embodiments, the RF rod 122 may have a square shape with recessed features 420 at the four corners of the RF rod 122, as shown in FIG. 4F. In some embodiments, the diameter of the RF rod 122 is between about 0.11 inches and about 0.14 inches. In some embodiments, the diameter of the RF rod 122 is between about 0.12 inches and about 0.13 inches.

[0029] 5A-5B illustrate various side profiles of an RF rod 122 according to at least some embodiments of the present disclosure. The inventors have recognized that increasing the cross-sectional area of ​​the top of the RF rod 122 or shortening the length of the RF rod 122 can reduce the impedance of the substrate support 108. In some embodiments, as shown in FIG. 5A, the RF rod 122 includes a top portion 510 and a bottom portion 520. In some embodiments, the diameter 512 of the top portion 510 is larger than the diameter of the bottom portion 520. FIG. 5B illustrates an RF rod 122 having a short length. In some embodiments, the length of the RF rod 122 can be about 7.5 to about 9 inches.

[0030] While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof.

Claims

1. 1. A substrate support for a process chamber, comprising: a pedestal having a support surface for supporting a substrate, one or more heating elements disposed therein, and an RF electrode disposed therein; a hollow shaft coupled to a lower surface of the pedestal; an RF rod extending through the hollow shaft and coupled to the RF electrode, the RF rod being plated with a material including gold, silver, or nickel, and coupled to an impedance adjustment device; A substrate support comprising:

2. The substrate support of claim 1 , wherein the impedance adjustment device is disposed radially inward of the hollow shaft.

3. The substrate support of claim 1 , wherein the RF rod has a non-circular cross-sectional shape.

4. The substrate support of claim 3 , wherein the RF rod has a polygonal cross-sectional shape.

5. The substrate support of claim 1 , wherein the RF rod includes an upper portion and a lower portion, the upper portion having a larger diameter than the lower portion.

6. The substrate support according to any one of claims 1 to 5, wherein the RF rod is brazed to the RF electrode with copper, gold, silver or nickel.

7. Substrate support according to any one of claims 1 to 5, wherein the RF rod has a non-uniform diameter along the length of the RF rod.

8. The substrate support of any one of claims 1 to 5, wherein the lower ends of the RF rods are bonded to a ceramic insulator.

9. The substrate support of any one of claims 1 to 5, wherein the RF rod has a diameter of about 0.11 inches to about 0.14 inches.

10. 6. The substrate support of claim 1, wherein the RF rod comprises a first material plated with a material comprising gold, silver or nickel, the first material being different from the material comprising gold, silver or nickel.

11. Substrate support according to any one of claims 1 to 5, wherein the impedance adjustment device comprises at least one of a variable inductor or a variable resistor.

12. The substrate support of claim 11 , wherein the RF rod is brazed to the RF electrode with copper, gold, silver or nickel.

13. The substrate support of any one of claims 1 to 5, wherein the RF electrode comprises a mesh.

14. a chamber body defining an interior volume therein; A substrate support according to any one of claims 1 to 5, arranged within the internal volume; A process chamber comprising:

15. The process chamber of claim 14 , wherein the impedance adjustment device is disposed within the interior volume.

16. 15. The process chamber of claim 14, wherein the impedance adjustment device comprises at least one of a variable inductor or a variable resistor.

17. 15. The process chamber of claim 14, wherein the RF rod is brazed to the RF electrode with copper, gold, silver, or nickel.

18. 15. The process chamber of claim 14, further comprising: a heating power supply coupled to the one or more heating elements; and one or more RF filters disposed between the heating power supply and the one or more heating elements.

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

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

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