WO2020222764A1

WO2020222764A1 - Ground strap assemblies

Info

Publication number: WO2020222764A1
Application number: PCT/US2019/029711
Authority: WO
Inventors: Shouqian Shao; Zonghui SU; Lai ZHAO; Jianhua Zhou; Fei Peng
Original assignee: Applied Materials, Inc.
Priority date: 2019-04-29
Filing date: 2019-04-29
Publication date: 2020-11-05
Also published as: JP2022537246A; KR20210148406A; CN114008755A; TW202102066A; JP7446335B2

Abstract

The present disclosure relates to methods and apparatus for plasma processing a substrate. In one embodiment, a substrate processing chamber includes a ground strap assembly. The ground strap assembly includes a ground strap and one or more connectors coupled to the substrate support and/or chamber body. Each connector has a first clamp member and a second clamp member. The ground strap is fastened between the first and second clamp members of each connector. An inner surface of each first and second clamp member couples to the ground strap and is coated with a dielectric coating. Modulation of the thickness and roughness of the inner surfaces enables tuning of the capacitance characteristics of the connectors

Description

GROUND STRAP ASSEMBLIES

BACKGROUND

Field

[0001] Embodiments of the present disclosure generally relate to methods and apparatus for processing substrates, such as semiconductor substrates, using plasma. More particularly, embodiments of the present disclosure relate to radio frequency (RF) ground strap assemblies for plasma processing chambers.

Description of the Related Art

[0002] Plasma enhanced chemical vapor deposition (PECVD) is used for processing substrates, such as semiconductor substrates, solar panel substrates, and flat panel display substrates. PECVD is generally carried out by introducing one or more precursor gases into a vacuum chamber having a substrate disposed therein on a substrate support. The precursor gases are directed towards a process volume through a gas distribution plate, typically situated near the top of the vacuum chamber. The precursor gases are energized (e.g., excited) into a plasma by applying a power, such as radio frequency (RF) power, to an electrode in the chamber by one or more power sources coupled to the electrode. The excited gas or gas mixture then reacts to form a material film layer on a surface of the substrate disposed on the substrate support. The material film layer may be, for example, a passivation layer, a gate insulator, a buffer layer, and/or an etch stop layer.

[0003] During processing, the substrate support is electrically grounded in order to eliminate any voltage drop across the substrate support, which would affect deposition uniformity of the material film layer across the surface of the substrate. Additionally, if the substrate support is not properly grounded, electrical arcing and the formation parasitic plasma between the substrate support and the chamber body may occur due to the high electric potential difference between the substrate support and the chamber body. This results in particle formation, metal contamination, non-uniform deposition, yield loss, and hardware damage. The parasitic plasma reduces the concentration and density of capacitively coupled plasma within the chamber, and thus reduces the deposition rate of material film layers.

[0004] To minimize the occurrence of arcing and parasitic plasma in a large area plasma chamber, the substrate support is typically grounded to the chamber body by thin and flexible ground straps to form an electrical current return path. However, conventional ground strap arrangements provide electrical return paths with considerable electrical inductance (e.g. impedance) at radio frequencies, such as 13.56 MHz and higher. Thus, a significant voltage potential difference between the substrate support and the chamber body still remains, leading to unwanted arcing and parasitic plasma formation at the periphery of the substrate support.

[0005] Thus, what is needed in the art are improved substrate processing apparatus having ground strap assemblies with reduced electrical impedance.

SUMMARY

[0006] The present disclosure relates to methods and apparatus for plasma processing a substrate. In one embodiment, a substrate processing chamber is provided. The substrate processing chamber includes a chamber body having one or more chamber walls partially defining a process volume and a chamber bottom coupled to the one or more chamber walls. The chamber bottom further includes a chamber connector coupled thereto, the chamber connector having a first clamping member coupled to a second clamping member by one or more fasteners. A substrate support is disposed in the process volume and includes a support connector coupled thereto. The support connector has a first clamping member coupled to a second clamping member by one or more fasteners. A ground strap is coupled to the substrate support by the support connector at a first end and to the chamber bottom by the chamber connector at a second end. One or more surfaces of the support connector and/or the chamber connector configured contact the ground strap have a dielectric coating formed thereon. [0007] In one embodiment, a ground strap assembly is provided. The ground strap assembly includes a chamber connector and a support connector each having a dielectric coating formed on one or more surfaces thereof. The ground strap assembly further includes a ground strap having a first end coupled to the support connector and a second end coupled to the chamber connector. The support connector and the chamber connector function as capacitors.

[0008] In one embodiment, a ground strap assembly is provided. The ground strap assembly includes a ground strap having a first end coupled to a support connector and a second end coupled to a chamber connector. The first and second ends of the ground strap are formed of a dielectric material, and the chamber and support connectors function as capacitors at the first and second ends.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0010] Figure 1 illustrates a cross-sectional view of a substrate processing system having one or more ground straps coupled to a substrate support therein, according to one embodiment of the disclosure.

[0011] Figure 2 illustrates a side view of an exemplary ground strap according to one embodiment of the disclosure.

[0012] Figure 3 illustrates a cross-sectional view of a portion of the substrate processing chamber of Figure 1. [0013] Figure 4A illustrates a cross-sectional view of a portion of a ground strap assembly according to one embodiment of the disclosure.

[0014] Figure 4B illustrates a cross-sectional view of a portion of a ground strap assembly according to one embodiment of the disclosure.

[0015] Figure 5 illustrates a cross-sectional view of a ground strap assembly according to one embodiment of the disclosure.

[0016] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

[0017] The present disclosure relates to methods and apparatus for plasma processing a substrate. In one embodiment, a substrate processing chamber includes a ground strap assembly. The ground strap assembly includes a ground strap and one or more connectors coupled to the substrate support and/or chamber body. Each connector has a first clamp member and a second clamp member. The ground strap is fastened between the first and second clamp members of each connector. An inner surface of each first and second clamp member couples to the ground strap and is coated with a dielectric coating. Modulation of the thickness, roughness, and the dielectric constant of the inner surfaces enables tuning of the capacitance characteristics of the connectors.

[0018] Embodiments herein are illustratively described below in reference to use in a PECVD system configured to process substrates, such as a PECVD system available from Applied Materials, Inc., Santa Clara, California. However, it should be understood that the disclosed subject matter has utility in other system configurations such as etch systems, other chemical vapor deposition systems, and any other system in which a substrate is exposed to a plasma within a process chamber. It should further be understood that embodiments disclosed herein may be practiced using process chambers provided by other manufacturers and chambers using differently types of substrates. It should also be understood that embodiments disclosed herein may be adapted for practice in other process chambers configured to process substrates of various shapes, sizes, and dimensions.

[0019] Figure 1 is a cross-sectional view of a substrate processing system 100, such as a PECVD apparatus, according to one embodiment. The substrate processing system 100 is configured to process a large area substrate 114 using plasma during the fabrication of liquid crystal displays (LCD’s), flat panel displays, organic light emitting diodes (OLED’s) or photovoltaic cells for solar cell arrays. The structures may include p-n junctions to form diodes for photovoltaic cells, metal oxide semiconductor field-effect transistors (MOSFETs), and thin film transistors (TFTs).

[0020] The substrate processing system 100 is configured to deposit a variety of materials on the large area substrate 114, including but not limited to dielectric materials, semiconductive materials, and insulating materials. For example, dielectric and semiconductive materials may include polycrystalline silicon, epitaxial silicon, amorphous silicon, microcrystalline silicon, silicon germanium, silicon oxide, silicon oxynitride, silicon nitride, and combinations thereof or derivatives thereof. The plasma processing system 100 is further configured to receive gases therein, including but not limited to precursor gases, purge gases, and carrier gases. For example, the plasma processing system may receive gas species such as hydrogen, oxygen, nitrogen, argon, helium, silane, and combinations thereof or derivatives thereof.

[0021] The substrate processing system 100 includes a substrate processing chamber 102 coupled to a gas source 104. The substrate processing chamber 102 includes chamber walls 106 and a chamber bottom 108 (collectively, a chamber body 101) that partially define a process volume 110. The process volume 110 is generally accessed through a sealable slit valve 112 in the chamber walls 106 that facilitates ingress and egress of the substrate 114 to and from the process volume 110. The chamber walls 106 and chamber bottom 108 are generally fabricated from aluminum, aluminum alloys, or other suitable materials for substrate processing. In one embodiment, the chamber walls 106 and chamber bottom 108 are coated with a protective barrier material to reduce effects of corrosion. For example, the chamber walls 106 and chamber bottom 108 may be coated with a ceramic material, a metal oxide material, or rare earth-containing material.

[0022] The chamber walls 106 support a lid assembly 116. A gas distribution plate 126 is suspended in the substrate processing chamber 102 from a backing plate 128 that is coupled to the lid assembly 116 or the chamber walls 106. A gas volume 140 is formed between the gas distribution plate 126 and the backing plate 128. The gas source 104 is connected to the gas volume 140 via a gas supply conduit 141. The gas supply conduit 141 , backing plate 128, and gas distribution plate 126 are generally formed from an electrically conductive material and are in electrical communication with one another. In one embodiment, the gas distribution plate 126 and backing plate 128 are manufactured from a unitary block of material. The gas distribution plate 126 is generally perforated such that process gases are uniformly distributed into the substrate processing volume 110.

[0023] A substrate support 118 is disposed within the substrate processing chamber 102 opposing the gas distribution plate 126 in a generally parallel manner. The substrate support 118 supports the substrate 114 during processing. Generally, the substrate support 118 is fabricated from conductive materials, such as aluminum, and encapsulates at least one temperature control device, which controllably heats or cools the substrate support 118 to maintain the substrate 114 at a predetermined temperature during processing.

[0024] The substrate support 118 has a first surface 120 and a second surface 122. The first surface 120 is opposite the second surface 122. A third surface 121 , which is perpendicular to the first surface 120 and the second surface 122, couples the first surface 120 and the second surface 122. The first surface 120 supports the substrate 114. The second surface 122 has a stem 124 coupled thereto. The stem 124 couples the substrate support 118 to an actuator (not shown) that moves the substrate support 118 between an elevated processing position (as shown) and a lowered position that facilitates substrate transfer into and out of the substrate processing chamber 102. The stem 124 also provides a conduit for electrical and thermocouple leads between the substrate support 118 and other components of the substrate processing system 100.

[0025] An RF power source 142 is generally used to generate a plasma between the gas distribution plate 126 and the substrate support 118. The RF power source 142 may generate an electric field between the gas distribution plate 126 and the substrate support 118 to form the plasma from the gases present between the gas distribution plate 126 and the substrate support 118. Various frequencies may be used. For example, the frequency may be between about 0.3 MHz and about 200 MHz, such as about 13.56 MHz. In one embodiment, the RF power source 142 is coupled to the gas distribution plate 126 via an impedance matching circuit 144 at a first output 146. A second output 148 of the impedance matching circuit 144 is further electrically coupled to the chamber body 101.

[0026] In one embodiment, a remote plasma source (not shown), such as an inductively coupled remote plasma source, may also be coupled between the gas source 104 and the gas volume 140. Between processing substrate, a cleaning gas may be provided to the remote plasma source. The cleaning gas may be excited to a plasma within the remote plasma source, forming a remote plasma. The excited species generated by the remote plasma source may be provided into the substrate processing chamber 102 to clean chamber components. The cleaning gas may be further excited by the RF power source 142 to reduce recombination of the dissociated cleaning gas species. Suitable cleaning gases include, but are not limited to, NF₃, F₂, and SF₆.

[0027] One or more ground straps 130 are electrically connected to the substrate support 118 at a top end 152 of each ground strap 130 and to the chamber bottom 108 at a bottom end 154 of each ground strap 130. In one embodiment, the ground straps 130 are electrically connected to the second surface 122 of the substrate support 118 at the top end 152. In further embodiments, the ground straps 130 are electrically connected to the third surface 121 at the top end 152. The substrate processing chamber 102 may include any suitable number of ground straps 130 for grounding the substrate support 118 to the chamber bottom 108, thus forming an RF current return path between the substrate support 118 and the chamber bottom 108 (five straps are shown in Figure 1). For example, one strap, two straps, three straps, four straps, five straps, or more may be used. The ground straps 130 are configured to shorten the path for RF current during processing and minimize arcing and parasitic plasma near the periphery of the substrate support 118.

[0028] The substrate support 118 includes one or more support connectors 132 coupled thereto. In one embodiment, the one or more support connectors 132 are coupled to the second surface 122 of the substrate support 118. In further embodiments, the one or more support connectors 132 are coupled to the third surface 121 of the substrate support 118. Five support connectors are shown in Figure 1. Other quantities of support connectors 132, however, are also contemplated depending on the number of ground straps 130 utilized.

[0029] Similarly, the chamber bottom 108 includes one or more chamber connectors 134 coupled thereto. In other embodiments, the one or more chamber connectors 134 are coupled to the chamber walls 106. Five chamber connectors are shown coupled to the chamber bottom 108 in Figure 1. Other quantities of chamber connectors 134, however, are also contemplated depending on the number of ground straps 130 utilized. According to one embodiment shown in Figure 1 , each of the ground straps 130 is coupled to the substrate support 118 via a support connector 132 at the top end 152 and to the chamber bottom 108 via a corresponding chamber connector 134 at the bottom end 154. The coupling of each ground strap 130 to a support connector 132 and a chamber connector 134 forms a ground strap assembly 150. [0030] Figure 2 is a side view of an exemplary ground strap 130. The body 232 of ground strap 130 is generally a rectangular piece of thin, flexible aluminum material having a top end 152 and a bottom end 154, with an optional slit 234 centrally located along the body 232 between the top end 152 and the bottom end 154. In one example, the ground strap 130 is further fabricated with one or more folds (not shown) located between the top end 152 and the bottom end 154. In another example, the one or more folds may form during processing when the substrate support 118 is raised and lowered between a home position and a processing position, thus bending the ground strap 130 and forming the one or more folds. In one embodiment, the ground strap 130 has a length L of between about 14 inches to about 30 inches, such as between about 18 inches and about 28 inches, such as between about 22 inches and about 24 inches. In one embodiment, the ground strap 130 has a width W of between about 0.5 inches and about 2 inches, such as between about 1 inch and about 1.5 inches. Figure 2 illustrates one example of a ground strap 130 suitable for the processing system described herein. The ground strap 130 is generally any suitable size, shape, and material conducive to substrate processing.

[0031] Figure 3 is a cross-sectional view of a portion 300 of the substrate processing chamber 102 of Figure 1. Figure 3 illustrates three ground strap assemblies 150 having ground straps 130 coupled to the substrate support 118 by the support connectors 132 and further coupled to the chamber bottom 108 by the chamber connectors 134. As depicted, each ground strap assembly 150 includes a single ground strap 130 coupled to a single support connector 132 and a single chamber connector 134. However, it is also contemplated that one or more ground straps 130 may be coupled to each support connector 132 and/or each chamber connector 134. For example, each support connector 132 and/or each chamber connector 134 may be coupled to two ground straps 130.

[0032] According to one embodiment, each support connector 132 and chamber connector 134 includes a first clamp member 362, 372 and a second clamp member 364, 374, respectively. The ground straps 130 are fastened between the first clamp member 362 and the second clamp member 364 of each support connector 132 at the top end 152 and between the first clamp member 362 and the second clamp member 364 of each chamber connector 134 at the bottom end 154. Fastening of the ground straps 130 is achieved via mechanical clamping force between the first clamp members 362, 372 and the second clamp members 364, 374.

[0033] Figure 4A illustrates the support connector 132 in greater detail. In one embodiment, the first clamp member 362 of the support connector 132 is an L-block having a main body 480 and an extension 482. The contact area is between about 0.5 square inches and about 3 square inches, such as between about 1 square inch and about 2 square inches, depending on the desired capacitance. The main body 480 has a major axis X substantially parallel to the second surface 122 of the substrate support 118. The extension 482 protrudes from an upper surface 481 of the main body 480 in a substantially perpendicular manner relative to the major axis X and contacts the second surface 122 on an upper surface 483 thereof. Thus, the upper surface 481 of the main body 480 does not directly contact the second surface 122 of the substrate support 118, and is disposed at a distance therefrom equal to a height E of the extension 482. In one embodiment, the upper surfaces 481 , 483 are substantially planar.

[0034] The main body 480 further contacts the second clamp member 364 on a lower surface 485 thereof when fastening the ground strap 130. In one embodiment, the lower surface 485 is substantially planar. In another embodiment, the lower surface 485 has a planar first portion 431 that is substantially parallel to the second surface 122 and a second portion 433 oriented at an angle ai relative to the second surface 122. For example, the second portion 433 is oriented at an angle ai between about 0 degrees and about 45 degrees relative to the first portion 431. In one embodiment, the lower surface 485 further includes a recess (not shown) formed therein and matching a protrusion (not shown) formed on an upper surface 487 of the second clamp member 364, or vice versa. The recess and the protrusion formed in the lower surface 485 and the upper surface 487 are shaped and sized to accommodate the dimensions of the ground strap 130, thus creating a pocket wherein the ground strap 130 is more securely fastened by the support connector 132.

[0035] In one embodiment, the upper surface 487 of the second clamp member 364 is substantially parallel to the lower surface 485 of the first clamp member 362. In one embodiment, the upper surface 487 has a planar first portion 435 that is substantially parallel to the lower surface 485 and a second portion 437 defined by a radial curve to accommodate for folding of the ground strap 130 when the substrate support 118 is raised and lowered between a home position and a processing position. In other embodiments, the second portion 437 is a planar surface disposed at an angle a₂ between about 0 degrees and about 45 degrees relative to the first portion 435. The second clamp member 364 further includes a lower surface 489 facing the chamber bottom 108. In one embodiment, the lower surface 489 is substantially planar.

[0036] The first clamp member 362 and the second clamp member 364 each comprise at least one set of fastener holes adapted to receive fasteners such as bolts, screws, or the like. For example, the first clamp member 362 includes a first set of fastener holes 456 adapted to receive at least one fastener 466 for coupling the first clamp member 362 to the substrate support 118. The first set of fastener holes 456 is disposed through the main body 480 and the extension 482 of the first clamp member 362. In one embodiment, the first clamp member 362 further includes a second set of fastener holes 458 aligned with a third set of fastener holes 460 disposed through the second clamp member 364. The second and third sets of fastener holes 458, 460 are adapted to receive at least one fastener 468 for coupling the second clamp member 364 to the first clamp member 362. In one embodiment, the second set of fastener holes 458 is only disposed through the main body 480 of the first clamp member 362 and not the extension 482. In one embodiment, the first clamp member 362 has only one set of fastener holes 458 aligned and adapted to receive at least one fastener 468 for coupling the first clamp member 362 to the substrate support 118 and to the second clamp member 364. The one or more sets of fastener holes described above are disposed near peripheral edges of the first and second clamp members 362, 364, such that the fasteners 466, 468 do not contact the ground strap 130 fastened therebetween.

[0037] Figure 4B illustrates the chamber connector 134 in greater detail. In one embodiment, each of the first clamp member 372 and the second clamp member 374 of the chamber connector 134 have a major axis X substantially parallel to the chamber bottom 108. In one embodiment, an upper surface 491 of the first clamp member 372 and a lower surface 499 of the second clamp member 374 are substantially planar. In one embodiment, each of a lower surface 495 of the first clamp member 372 and an upper surface 497 of the second clamp member 374 have a first portion that is substantially parallel to the chamber bottom 108 and a second portion oriented at an angle relative to the first portion. For example, the lower surface 495 has a substantially parallel first portion 421 and a second portion 423 oriented at an angle bi between about 0 degrees and about 45 degrees relative to the first portion 421. Similarly, the upper surface 497 has a substantially parallel first portion 425 and a second portion 427 oriented at an angle b₂ between about 0 degrees and about 45 degrees relative to the first portion 425.

[0038] In one embodiment, the lower surface 495 further includes a recess (not shown) formed therein and matching a protrusion (not shown) formed on the upper surface 497, or vice versa. The recess and the protrusion formed in the lower surface 495 and the upper surface 497 are shaped and sized to accommodate the dimensions of the ground strap 130, thus creating a pocket wherein the ground strap 130 is more securely fastened by the chamber connector 134. It is further contemplated that the chamber connector 134 may be substantially similar in size, shape, and configuration to the support connector 132.

[0039] Similar to the support connector 132, the first clamp member 372 and the second clamp member 374 each comprise at least one set of fastener holes adapted to receive fasteners such as bolts, screws, or the like. For example, the second clamp member 374 includes a first set of fastener holes 446 adapted to receive at least one fastener 462 for coupling the second clamp member 374 to the chamber bottom 108. In one embodiment, the second clamp member 374 further includes a second set of fastener holes 448 aligned with a third set of fastener holes 450 disposed through the first clamp member 372. The second and third sets of fastener holes 448, 450 are adapted to receive at least one fastener 464 for coupling the second clamp member 374 to the first clamp member 372. In one embodiment, the second clamp member 374 has only one set of fastener holes 448 aligned and adapted to receive at least one fastener 464 for coupling the second clamp member 374 to the chamber bottom 108 and to the first clamp member 372. The one or more sets of fastener holes described above are disposed near peripheral edges of the first and second clamp members 372, 344, such that the fasteners 462, 464 do not contact the ground strap 130 fastened therebetween.

[0040] Generally, the components of the ground strap assembly 150 are formed of a conductive material such as aluminum, nickel, nickel alloy, or the like. In one embodiment, the first clamp members 362, 372 and the second clamp members 364, 374 further include a dielectric coating 490 formed on desired surfaces thereof. The dielectric coating 490 enables the support connector 132 and/or the chamber connector 134 to function as a capacitor along an electrical current return path provided by the ground strap assembly 150.

[0041] In one embodiment, the dielectric coating 490 is formed on surfaces of the support connector 132 and/or the chamber connector 134 configured to contact and fasten the ground strap 130 therebetween. For example, the dielectric coating 490 is formed on the lower surface 485 of the first clamp member 362 and the upper surface 487 of the second clamp member 364. Alternatively or additionally, the dielectric coating 490 is formed on the lower surface 495 of the first clamp member 372 and the upper surface 497 of the second clamp member 374. The dielectric coating 490 may also be optionally formed on the lower surface 489 of the second clamp member 364 and/or the upper surface 491 of the first clamp member 372, in addition to the surfaces configured to contact the ground strap 130. The dielectric coating 490 formed on the lower surface 489 and/or the upper surface 491 may further be utilized to modulate capacitance characteristics of the components of the ground strap assembly 150.

[0042] The dielectric coating 490 is formed of any suitable dielectric material, including but not limited to polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), Teflon, yttrium oxide, or the like. In some embodiments, the dielectric coating 490 is formed by spread coating. In one embodiment, the dielectric coating 490 is formed by anodizing desired surfaces of the support and chamber connectors 132, 134. For example, the dielectric coating 490 may be formed of anodized aluminum.

[0043] In one embodiment, the dielectric coating 490 has a thickness of between about 10 pm and about 100 pm, such as between about 20 pm and about 80 pm, such as between about 40 pm and about 60 pm. For example, the dielectric coating 490 has a thickness of about 50 pm. In one embodiment, the dielectric coating 490 further has a surface roughness value of between about 0 pm and about 5 pm, such as between about 2 pm and about 4 pm. By modulating the thickness and surface roughness of the dielectric coating 490, the capacitance characteristics of the support connector 132 and the chamber connectors 134 may be precisely controlled, thus enabling modulation of the impedance across the length of the ground strap assembly 150 and ultimately the voltage potential difference. For example, by reducing the thickness of the dielectric coating 490 formed on the support connector 132 or the chamber connector 134, capacitance of the component may therein be increased, thus reducing total impedance across the ground strap assembly 150 and resulting in a reduction of the voltage potential difference between the substrate support 118 and the chamber body 108. [0044] Figure 5 is a cross-sectional view of a ground strap assembly 550. The ground strap assembly 550 is substantially similar to the ground strap assembly 150 but includes two ground straps 130, 131 coupled together in an overlapping manner by a dielectric fastener 592 at a junction 596. The ground strap 130 is coupled to the support connector 132 at the top end 152 and the ground strap 131 is coupled to the chamber connector 134 at the bottom end 154. The support connector 132 and the chamber connector 134 are substantially similar to the embodiments described above and may include the dielectric coating 490 formed on desired surfaces thereof. For example, the dielectric coating 490 is formed on surfaces of the support connector 132 and the chamber connector 134 contacting the ground straps 130, 131 when clamped therein.

[0045] In one embodiment, the dielectric fastener 592 includes a bolt, screw, or the like and a matching nut to couple the ground straps 130, 131 therebetween. Two or more plates 594 may further be disposed on opposing sides of the ground straps 130, 131 at the junction 597 to secure the ground straps 130,131 against one another. The plates 594 may be formed of any suitable metallic material, including but not limited to stainless steel, aluminum, nickel or the like. Although depicted as a screw or bolt in Figure 5, the dielectric fastener 592 is generally any suitable coupling mechanism.

[0046] The dielectric fastener 592 is formed of any suitable dielectric material, including but not limited to PTFE, PEEK, Torlon, or the like. In one embodiment, the dielectric fastener 592 is formed of the same material as the dielectric coating 490. Similar to the dielectric coating 490, the dielectric fastener 592 functions as a capacitor along the electrical current return path provided by the ground strap assembly 550. By modulating the thickness of the dielectric fastener 592 and the contact area between the dielectric fastener 592 and the ground straps 130, 131 , the capacitance characteristics of the dielectric fastener 592 may be precisely controlled, thus enabling further modulation of the impedance across the length of the ground strap assembly 550. In one embodiment, the dielectric fastener 592 is utilized as a capacitor in addition to the support connector 132 and/or the chamber connector 134 having the dielectric coating 490 formed thereon. In one embodiment, the dielectric fastener 592 is utilized as a capacitor in place of the support connector 132 and/or the chamber connector 134. Thus, the ground strap assembly 550 may have any combination of capacitors at one or more locations along the ground strap assembly 550.

[0047] In the operation of a conventional plasma processing chamber, the substrate support provides a return path for RF power supplied to the gas distribution plate and the substrate support itself, creating a voltage potential difference between the substrate support and surrounding inner surfaces of the chamber body. This potential difference inadvertently causes electrical arcing between the substrate support and surrounding surfaces, such as the chamber walls. The magnitude of the potential difference, and thus the amount of arcing between the substrate support and chamber walls, is partially dependent on the resistance and size of the substrate support. Arcing is deleterious and results in particle contamination, film deposition variance, substrate damage, chamber component damage, yield loss, and system downtime.

[0048] The utilization of ground straps coupled to the substrate support and chamber body provides an alternate RF return path for the RF power supplied to either the substrate support or gas distribution plate, thus reducing the probability of electrical arcing between the substrate support and chamber body. However, conventional ground strap assemblies still provide significant electrical resistance and impedance along the alternate RF return path they were meant to create, forming a sufficient voltage potential difference between the substrate support and chamber body to cause arcing therebetween.

[0049] By forming a dielectric layer on the ground strap connectors and utilizing the connectors as capacitors, the voltage potential difference between the substrate support and the chamber body is significantly reduced and thus RF grounding efficiency is increased. As a result, the reduced voltage potential difference eliminates or diminishes arcing between the substrate support and the chamber body.

[0050] Furthermore, the reduced voltage potential difference reduces the formation of parasitic plasma during processing. During deposition processes, the generated plasma generally leaks to other parts of the chamber, becoming parasitic plasma that forms undesired films on various chamber components, such as the chamber walls, the chamber bottom, the substrate support, and the plurality of ground straps. The formation of parasitic plasma typically occurs between the outer edge of the substrate support or gas distribution plate and the surrounding chamber walls, or beneath the substrate support. Parasitic plasma is harmful because such plasma negatively influences the plasma uniformity of thin films deposited on the substrate and may accelerate corrosion of chamber components such as the ground straps themselves. Reducing or eliminating the formation of parasitic plasma during processing thus extends the lifetime of the ground straps 130 as well as other chamber components.

[0051] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:

1. A substrate processing chamber, comprising:

a chamber body, comprising:

one or more chamber walls at least partially defining a process volume; and

a chamber bottom coupled to the one or more chamber walls, the chamber bottom having a chamber connector coupled thereto, the chamber connector further comprising:

a first clamping member coupled to a second clamping member by one or more fasteners;

a substrate support disposed in the process volume, the substrate support having a support connector coupled thereto, the support connector further comprising:

a first clamping member coupled to a second clamping member by one or more fasteners; and

a ground strap having a first end and a second end, the first end coupled to the substrate support at the support connector and the second end coupled to the chamber bottom at the chamber connector, wherein one or more surfaces of the support connector and/or the chamber connector configured to contact the ground strap have a dielectric coating formed thereon.

2. The chamber of claim 1 , wherein the dielectric coating is formed of anodized aluminum.

3. The chamber of claim 1 , wherein the dielectric coating is formed of PTFE.

4. The chamber of claim 1 , wherein the dielectric coating has a thickness between about 10 pm and about 100 pm.

5. The chamber of claim 2, wherein the dielectric coating has a thickness between about 10 pm and about 100 pm.

6. The chamber of claim 1 , wherein the dielectric coating has a surface roughness between about 0 and about 5 urn.

7. The chamber of claim 2, wherein the dielectric coating has a surface roughness between about 0 and about 5 urn.

8. The chamber of claim 1 , wherein the dielectric coating is further formed on one or more surfaces of the support connector and/or the chamber connector not configured to contact the ground strap.

9. A ground strap assembly, comprising:

a chamber connector having a dielectric coating formed on one or more surfaces thereof;

a support connector having a dielectric coating formed on one or more surfaces thereof; and

a ground strap having a first end and a second end, the first end coupled to the support connector and the second end coupled to the chamber connector, wherein the chamber connector and the support connector function as capacitors.

10. The ground strap assembly of claim 9, wherein the support connector and the chamber connector are formed of aluminum.

11. The ground strap assembly of claim 10, wherein the dielectric coating is formed of anodized aluminum.

12. The ground strap assembly of claim 11 , wherein the dielectric coating has a thickness between about 10 pm and about 100 pm.

13. The ground strap assembly of claim 10, wherein the dielectric coating is formed of PTFE.

14. The ground strap assembly of claim 9, wherein each of the chamber connector and the support connector include a first clamping member and a second clamping member coupled together by one or more fasteners.

15. A ground strap assembly, comprising:

a chamber connector;

a support connector; and

a ground strap having a first end and a second end, the first end coupled to the support connector and the second end coupled to the chamber connector, the first and second ends of the ground strap being formed of a dielectric material, wherein the chamber connector and the support connector function as capacitors at the first and second ends.