BACKGROUND

Field

[0001] Embodiments described herein generally relate to methods and apparatus for processing large area substrates using plasma. More particularly, embodiments described herein relate to a modulated radio frequency (RF) current return path for a plasma processing chamber.

Description of the Related Art

[0002] Plasma enhanced chemical vapor deposition (PECVD) is generally employed to deposit thin films on substrates, such as semiconductor substrates, solar panel substrates, and liquid crystal display (LCD) and organic light emitting diode (OLED) substrates used in display manufacture. PECVD is generally accomplished by introducing a precursor gas into a vacuum chamber having a substrate disposed on a susceptor or substrate support. The precursor gas is typically directed through a gas distribution plate situated near the top of the vacuum chamber. The precursor gas in the vacuum chamber is energized (e.g., excited) into a plasma by applying a radio frequency (RF) power to the chamber from one or more RF sources coupled to the chamber. The excited gas reacts to form a thin film of material on a surface of the substrate (or devices formed thereon). The gas distribution plate is generally connected to a RF power source and the susceptor is typically connected to the chamber body providing a RF current return path.

[0003] In the manufacture of OLED devices, PECVD process are generally used to form a thin film on a plurality of OLED devices formed on a substrate. The thin film is utilized to encapsulate and/or hermetically seal the devices (known as thin film encapsulation (TFE)). Uniformity is generally desired in these thin films deposited on the OLED devices using PECVD processes. When the thin films are not uniform across the substrate area, the yield may be decreased. It has been found that the non-uniformity is related to plasma density uniformity, which is affected by RF return. [0004] Therefore, what is needed is an improved RF return scheme for large area substrates.

SUMMARY

[0005] Embodiments of the disclosure generally relate to a method and apparatus for plasma processing a substrate. More particularly, embodiments of described herein provide a plasma processing chamber having one or more radio frequency (RF) grounding or return devices adapted to provide an advantageous RF return path.

[0006] In one embodiment, a process kit is provided. The process kit includes a susceptor having a rectangular body made of an electrically conductive material, the rectangular body comprising a perimeter that includes a first major side opposite to a second major side, and a first minor side opposite to a second minor side, wherein each of the minor sides are adjacent to and extend between the first major side and the second major side interfacing at a respective corner. The susceptor also includes a plurality of grounding devices coupled to the perimeter of the rectangular body outside of the respective corners of the rectangular body, wherein the plurality of grounding devices includes four or more side grounding devices coupled to each of the first major side, the second major side, the first minor side and the second minor side; and eight or more bottom grounding devices coupled to each of the first major side, the second major side, the first minor side and the second minor side.

[0007] In another embodiment, a process kit is provided. The process kit includes a susceptor having a rectangular body made of an electrically conductive material, the rectangular body comprising a perimeter that includes a first major side opposite to a second major side, and a first minor side opposite to a second minor side, wherein each of the minor sides are adjacent to and extend between the first major side and the second major side interfacing at a respective corner. The susceptor also includes a bracket coupled to the perimeter of the rectangular body, and a plurality of grounding devices coupled to the bracket within an electrical grounding length of each of the first and second major sides and each of the first and second minor sides, wherein the plurality of grounding devices includes four or more side grounding devices coupled to each of the first major side, the second major side, the first minor side and the second minor side; and eight or more bottom grounding devices on each of the first major side, the second major side, the first minor side and the second minor side.

[0008] In another embodiment, a plasma processing system is provided. The plasma processing system includes a chamber, a first electrode disposed within the chamber, the first electrode facilitating generation of a plasma within the chamber and movable relative to a second electrode within the chamber. The first electrode comprises a rectangular body made of an electrically conductive material, the rectangular body comprising a perimeter that includes a first major side opposite to a second major side, and a first minor side opposite to a second minor side, wherein each of the minor sides are adjacent to and extend between the first major side and the second major side interfacing at a respective corner. The first electrode also comprises a plurality of grounding devices coupled to the perimeter of the rectangular body outside of the respective corners of the rectangular body, wherein the plurality of grounding devices includes four or more side grounding devices coupled to each of the first major side, the second major side, the first minor side and the second minor side; and eight or more bottom grounding devices on each of the first major side, the second major side, the first minor side and the second minor side.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the disclosure can be understood in detail, a more particular description as described herein, 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 typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0010] Figure 1A is a schematic cross-sectional view of one embodiment of a plasma processing system.

[0011] Figure 1B is a schematic cross-sectional view of another embodiment of the plasma processing system shown in Figure 1A. [0012] Figure 2 is an isometric view of one embodiment of a side grounding device.

[0013] Figure 3 is an isometric rear side view of a portion of a bracket for coupling grounding devices.

[0014] Figure 4 is a schematic cross-sectional top view of the chamber body showing a top plan view of the susceptor.

[0015] Figures 5A-5C are schematic isometric views of various embodiments of grounding devices disposed on the bracket on the perimeter of a susceptor.

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

DETAILED DESCRIPTION

[0017] Embodiments of the present disclosure generally relate to a method and apparatus for processing substrates using plasma and/or cleaning components using plasma. A process kit is disclosed which includes a susceptor having various grounding devices coupled thereto to enable a radio frequency (RF) return path. Embodiments described herein relate to methods of enhancing plasma formation and depositing materials onto a substrate by providing an improved ground or return path for electrical current. In the description that follows, reference will be made to a plasma enhanced chemical vapor deposition (PECVD) chamber, but it is to be understood that the embodiments herein may be practiced in other chambers as well, including physical vapor deposition (PVD) chambers, etching chambers, semiconductor processing chambers, solar cell processing chambers, and organic light emitting display (OLED) processing chambers to name only a few. Suitable chambers that may be used are available from AKT America, Inc., a subsidiary of Applied Materials, Inc., Santa Clara, California. It is to be understood that the embodiments discussed herein may be practiced in chambers available from other manufacturers as well. [0018] The present disclosure may be utilized for processing substrates of any size or shape. However, the present disclosure provides particular advantage in substrates having a plan surface area of about 15,600 cm ² and including substrates having a plan surface area of about a 90,000 cm ² surface area (or greater). The increased size of the substrate surface area presents challenges in uniform processing due to the increased difficulty in providing a suitable ground path. Embodiments described herein provide a solution to these challenges during processing of the larger substrate sizes.

[0019] Figure 1A is a schematic cross-sectional view of one embodiment of a plasma processing system 100. The plasma processing system 100 is configured to process a large area substrate 101 using plasma in forming structures and devices on the large area substrate 101 for use in the fabrication of liquid crystal displays (LCD’s), flat panel displays, organic light emitting diode (OLED) devices, or photovoltaic cells for solar cell arrays. The substrate 101 may be thin sheet of metal, plastic, organic material, silicon, glass, quartz, or polymer, among others suitable materials. The plasma processing system 100 may be configured to deposit a variety of materials on the large area substrates 101, including but not limited to dielectric materials ( e.g ., S1O2, SiOxN _y , derivatives thereof or combinations thereof), semiconductive materials {e.g., Si and dopants thereof), or barrier materials {e.g., SiNx, SiOxN _y or derivatives thereof). Specific examples of dielectric materials and semiconductive materials that are formed or deposited by the plasma processing system 100 onto the large area substrates may include epitaxial silicon, polycrystalline silicon, amorphous silicon, microcrystalline silicon, silicon germanium, germanium, silicon dioxide, silicon oxynitride, silicon nitride, dopants thereof {e.g., B, P, or As), derivatives thereof or combinations thereof. The plasma processing system 100 is also configured to receive gases such as argon, hydrogen, nitrogen, helium, or combinations thereof, for use as a purge gas or a carrier gas {e.g., Ar, H2, N2, He, derivatives thereof, or combinations thereof). One example of depositing silicon thin films on the large area substrate 101 using the system 100 may be accomplished by using silane as a processing gas in a hydrogen carrier gas.

[0020] As shown in Figure 1A, the plasma processing system 100 generally comprises a chamber body 102 including a bottom 117a and sidewalls 117b that at least partially defines a processing volume 111. A susceptor 104 is disposed in the processing volume 111. The susceptor 104 is adapted to support the substrate 101 on a top surface during processing. The susceptor 104 is coupled to an actuator 138 adapted to move the susceptor at least vertically to facilitate transfer of the substrate 101 and/or adjust a distance D between the substrate 101 and a showerhead assembly 103. One or more lift pins 110a-110d may extend through the susceptor 104. The lift pins 110a-110d are adapted to contact the bottom 117a of the chamber body 102 and support the substrate 101 when the susceptor 104 is lowered by the actuator 138 in order to facilitate transfer of the substrate 101, as shown in Figure 1B. In a processing position as shown in Figure 1A, the lift pins 110a-110d are adapted to be flush with or slightly below the upper surface of the susceptor 104 to allow the substrate 101 to lie flat on the susceptor 104.

[0021] The substrate 101 and/or the susceptor 104 may have a surface area greater than about 5 square meters, such as about 5.5 square meters, or greater. In some embodiments, the substrate 101 and/or the susceptor 104 may include dimensions of about 2200 mm (on a minor side) by about 2500 mm (on a major side), or greater. The structures formed on the substrate 101 may be OLED devices, thin film transistors or p-n junctions to form diodes for photovoltaic cells.

[0022] The showerhead assembly 103 is configured to supply a processing gas to the processing volume 111 from a processing gas source 122. The plasma processing system 100 also comprises an exhaust system 118 configured to apply negative pressure to the processing volume 111. The showerhead assembly 103 is generally disposed opposing the susceptor 104 in a substantially parallel relationship.

[0023] In one embodiment, the showerhead assembly 103 comprises a gas distribution plate 114 and a backing plate 116. The backing plate 116 may function as a blocker plate to enable formation of a gas volume 131 between the gas distribution plate 114 and the backing plate 116. The gas source 122 is connected to the gas distribution plate 114 by a conduit 134. In one embodiment, a remote plasma source 107 is coupled to the conduit 134 for supplying a plasma of activated gas through the gas distribution plate 114 to the processing volume 111. The plasma from the remote plasma source 107 may include activated gases for cleaning chamber components disposed in the processing volume 111.

[0024] The gas distribution plate 114, the backing plate 116, and the conduit 134 are generally formed from electrically conductive materials and are in electrical communication with one another. The chamber body 102 is also formed from an electrically conductive material. The chamber body 102 is generally electrically insulated from the showerhead assembly 103. In one embodiment, the showerhead assembly 103 is mounted on the chamber body 102 by an insulator 135.

[0025] In one embodiment, the susceptor 104 is also electrically conductive, and the susceptor 104 and the showerhead assembly 103 are configured to be opposing electrodes for generating a plasma 108a of processing gases therebetween during processing and/or a pre-treatment or post-treatment process. Additionally, the susceptor 104 and the showerhead assembly 103 may be utilized to support a plasma 108b (Figure 1B) of cleaning gases during a cleaning process.

[0026] A radio frequency (RF) power source 105 is generally used to generate the plasma 108a between the showerhead assembly 103 and the susceptor 104 before, during and after processing, and may also be used to maintain energized species or further excite cleaning gases supplied from the remote plasma source 107. In one embodiment, the RF power source 105 is coupled to the showerhead assembly 103 by a first connection 106a of an impedance matching circuit 121. A second connection 106b of the impedance matching circuit 121 is electrically connected to the chamber body 102.

[0027] In one embodiment, the plasma processing system 100 includes a plurality of first RF devices 109a and a plurality of second RF devices 109b. Each of the first RF devices 109a and second RF devices 109b are coupled between the susceptor 104 and a grounded component of the chamber body 102. In one embodiment, the plurality of RF devices 109a and 109b are configured to control the return path for returning RF current during processing and/or a chamber cleaning procedure. [0028] Each of the first RF devices 109a may be referred to as side grounding devices 112. Each of the side grounding devices 112 are configured to selectively contact and/or provide a ground path between a side of the susceptor 104 and the chamber sidewall 117b. Additionally, each of the second RF devices 109b may be referred to as bottom grounding devices 113. Each of the bottom grounding devices 113 are configured to provide a return path between the susceptor 104 and the chamber bottom 117a. In some embodiments, each of the side grounding devices 112 and the bottom grounding devices 113 are coupled to an extended member 119 electrically coupled to the susceptor 104. The extended member 119 may be a separate member coupled to a perimeter of the susceptor 104, or a structure that includes a perimeter of the susceptor 104.

[0029] Each of the side grounding devices 112 include a movable conductive member 120 that is adapted to contact a ledge 124 that is electrically coupled to the sidewall 117b. Each of the side grounding devices 112 may be selectively activated to be open or closed to electrical current. In the closed position (shown in Figure 1A), each of the side grounding devices 112 are utilized to provide a RF conductive medium between the susceptor 104 and a component of the chamber body 102 for the RF return path. In the open position (shown in Figure 1 B), each of the side grounding devices 112 are not electrically coupled to the chamber component (i.e., a component of the chamber body 102 that is in electrical communication with the RF power source 105). In one aspect, the open/closed characteristic of each of the side grounding devices 112 may be controlled by the elevation of the susceptor 104 relative to the showerhead assembly 103 (i.e., elevation relative to the ledges 124).

[0030] One embodiment of an RF current path during substrate processing is schematically illustrated by arrows in Figure 1A. The RF current generally travels from a first lead 123a of the RF power source 105 to the first output 106a of the impedance matching circuit 121, then travels along an outer surface of the conduit 134 to a back surface of the backing plate 116, then to a front surface of the gas distribution plate 114. From the front surface of the gas distribution plate 114, the RF current goes through plasma 108a and reaches a top surface of the substrate 101 or the susceptor 104, then through the side grounding devices 112 and/or the bottom grounding devices 113 to an inner surface 125 of the chamber body 102. From the inner surface 125, the RF current returns to a second lead 123b of the RF power source 105 from the impedance matching circuit 121.

[0031] In one embodiment, the return path of the RF current during processing may be dependent on a spacing between the susceptor 104 and the showerhead assembly 103, which is depicted as a distance D. The spacing is controlled by the elevation of the susceptor 104. In one embodiment, the distance D is between about 200 mils to about 2000 mils during processing. At this spacing (e.g., elevation of the susceptor 104), the side grounding devices 112 and the bottom grounding devices 113 may both remain electrically coupled to the RF power source 105. In this embodiment, the RF return path taken by the RF current may be based on the electrical properties and positioning of the side grounding devices 112 and the bottom grounding devices 113. The electrical properties include resistance, impedance and/or conductance of the side grounding devices 112 and the bottom grounding devices 113. For example, since the side grounding devices 112 are closer and have less impedance for the RF current returning to the second lead 123b of the RF power source 105, the RF current flows predominantly through the side grounding devices 112 while little or no RF current flows through the bottom grounding devices 113.

[0032] Figure 1 B is a schematic cross-sectional view of the plasma processing system 100 shown in Figure 1A. In this Figure, the plasma processing system 100 is shown without a substrate to depict a chamber cleaning procedure, and arrows are shown to schematically depict RF current flow. In this embodiment, energized cleaning gases are flowed to the showerhead assembly 103 and the processing volume 111 from the remote plasma source 107 to supply a plasma 108b within the processing volume 111. During chamber cleaning, the susceptor 104 is displaced away from the showerhead assembly 103 and RF power from the RF power source 105 may be applied to the processing volume 111 to maintain or further energize the cleaning gas from the remote plasma source 107. In one embodiment, the spacing or distance D of the susceptor 104 relative to the showerhead assembly 103 during chamber cleaning is greater than the spacing or distance D of the susceptor 104 relative to the showerhead assembly 103 during processing. In one embodiment, the distance D between the susceptor 104 and the showerhead assembly 103 during a cleaning process is between about 200 mils to about 5000 mils, or greater.

[0033] In one embodiment, the side grounding devices 112 may be electrically or physically disconnected from the susceptor 104 such that returning RF current flows solely across the bottom grounding devices 113. In one embodiment, the elevation of the susceptor 104 causes a condition that substantially prevents RF current from passing through the side grounding devices 112. In one embodiment, the side grounding devices 112 are detached from the sidewall 117b and the susceptor 104 when the susceptor 104 is in this lowered position, thereby creating an RF open condition in the side grounding devices 112.

[0034] Figure 2 is an isometric view of one embodiment of a side grounding device 112 coupled to a perimeter 200 of the susceptor 104. The side grounding device 112 is shown coupled to a bracket 205 (e.g., the extended member 119 shown in Figures 1A and 1B). The susceptor 104 includes a body 210 made of an electrically conductive material, such as aluminum. The bracket 205 comprises an electrically conductive material, such as aluminum, that is electrically connected to the body 210. In one embodiment, the bracket 205 is configured as a bar that is coupled to a susceptor 104. The bracket 205 includes an extended base member 215 that protrudes from the perimeter 200 of the susceptor 104 at select locations. The extended base member 215 houses and/or supports the side grounding device 112 at these select locations.

[0035] The side grounding device 112 includes the movable conductive member 120 described in Figures 1A and 1B. The extended base member 215 includes an opening 220 adapted to receive a first shaft 222. The first shaft 222 is movably disposed through the opening 220 to provide relative movement between the base member 215 and the first shaft 222. The first shaft 222 is coupled to a second shaft 224 that is received inside a spring form 226. A collar 228 is coupled to the second shaft 224 to provide a base for the spring form 226. In one embodiment, the first shaft 222 is movable to any position within a travel distance indicated as 230 in Figure 2. The travel distance 230 corresponds to the distance range that the susceptor 104 may travel during various processes while maintaining electrical contact or grounding potential between the susceptor 104 and the chamber body 102.

[0036] The movable conductive member 120 includes at least one elastic portion, shown in this embodiment as spring form 226 as well as spring forms 232A and 232B. Spring forms 226, 232A and 232B provide elasticity to the movable conductive member 120. Spring forms 232A and 232B additionally provide a conductive path for electrical current.

[0037] In some embodiments, the spring forms may be in the form of a flat spring, a coil spring, a compression spring or other flexible spring device or spring form. In one embodiment, the spring forms 232A and 232B comprise a metallic material or metallic alloy, which may additionally be coated, wrapped or clad with a conductive material. Examples of metals and metal alloys include nickel, stainless steel, titanium, a MONEL ^® material, a HASTELLOY ^® material, a HAYNES ^® alloy, such as a HAYNES ^® 242 ^® material, beryllium copper, or other conductive elastic materials. Examples of conductive materials for the coating, wrapping or cladding include aluminum, anodized aluminum, or other coating, film, or sheet material. In one embodiment, each of the spring forms 232A and 232B comprise a nickel or titanium alloy sheet material that is wrapped or covered with an aluminum material. In another embodiment, the spring form 226 comprises a Ni-Mo-Cr alloy, such as a HASTELLOY ^® material or a HAYNES ^® 242 ^® material. The Ni-Mo-Cr alloy material may be coated, wrapped or clad with aluminum or a conductive metallic sheath or coating. In one embodiment, the spring form 226 comprises a MONEL ^® 400 material while the spring forms 232A and 232B comprise a HAYNES ^® 242 ^® material wrapped with an aluminum foil.

[0038] In one embodiment, the spring forms 232A and 232B may be a continuous single sheet material or a single flat spring having two ends 234A, 234B. Alternatively, the spring forms 232A and 232B may be two separate, discontinuous pieces of sheet material or two flat springs coupled at respective ends at a contact pad 236. In either embodiment, the spring forms 232A and 232B are electrically coupled to the contact pad 236, which is made of an electrically conductive material. When the side grounding device 112 is in the closed position (shown in Figure 1A), RF current is conducted from the body 210 via the bracket 205, on or through the spring forms 232A and/or 232B, and to the chamber body 102 via the contact pad 236 in contact with the ledge 124.

[0039] The collar 228 may comprise a nut or include a threaded portion for a set screw that is adapted to fix to the second shaft 224 thereby capturing the spring form 226. The second shaft 224 may be of a reduced dimension, such as a diameter, to allow the spring form 226 to fit thereover. In this embodiment, the second shaft 224, the spring form 226 and the collar 228 are disposed or housed within a tubular member 238. As the spring form 226, the second shaft 224 and the collar 228 are made of a conductive material, the tubular member 238, which is made of a dielectric material, electrically insulates the conductive members therein. In this manner, arcing, or arcing potential, is reduced. .

[0040] Figure 3 is an isometric rear side view of a portion of the bracket 205. The bracket 205 is shown as viewed from a side thereof that would couple to the perimeter 200 of the susceptor 104 (both shown in Figure 2). A plurality of extended base members 215 are shown at periodic intervals along a length of the bracket 205. Two or more side grounding devices 112 are shown coupled to the bracket 205 with an empty base member 300 therebetween. Also shown is a plurality of bottom grounding devices 113 (i.e., second RF devices 109b) coupled directly to the bracket 205.

[0041] Each of the bottom grounding devices 113 may be spring forms, straps, wires, or cables adapted to provide a RF conductive medium between the susceptor 104 and a grounded component of the chamber body 102 (both shown in Figures 1A and 1B). In one embodiment, the bottom grounding devices 113 are configured as straps made of, or coated with, a flexible conductive material. The material of the bottom grounding devices 113 may be aluminum, or comprise one or more of the same material combination as described in conjunction with the spring forms of the side grounding devices 112.

[0042] Each of the bottom grounding devices 113 may be coupled directly to the extended base members 215 and/or a bottom surface 305 of the bracket 205. In one embodiment, at least a portion of the bottom grounding devices 113 are coupled to a recessed region 312 of the bracket 205 between adjacent extended base members 215. While the movable conductive member 120 may alternate between adjacent extended base members 215, the bottom grounding devices 113 are consecutively coupled to the bracket 205 at a select spacing. In one example, the side grounding device 112 include a spacing 310 of about 21 inches to about 25 inches, such as about 22 inches to about 24 inches, for example 23.5 inches. In contrast, the bottom grounding devices 113 include a spacing 315 of about 9 inches to about 12 inches, such as about 10 inches to about 11 inches. The term “about” in this context means +/- 0.1 inches.

[0043] Each of the bottom grounding devices 113 include a first end 320 and a second end 325. The first end 320 couples to the bracket 205 using one or more fasteners, such as a screw or bolt, in order to fasten the first end 320 to the bracket 205. The second end 325 includes a fastener interface 330 to facilitate coupling thereof to a surface of the chamber bottom 117a (shown in Figures 1A and 1 B). The fastener interface 330 may be a slot or elongated hole adapted to receive a fastener, such as a bolt or screw, in order to fasten the second end 325 to the chamber body.

[0044] Figure 4 is a schematic cross-sectional top view of the chamber body 102 showing a top plan view of the susceptor 104 (having a substrate 101 thereon). Figure 4 also shows sectional views of the chamber body 102 (along the plane of the substrate 101) in order to show one embodiment of the positioning of the side grounding devices 112.

[0045] The chamber body 102 is shown with the susceptor 104 disposed therein and the side grounding devices 112 are disposed in a space between an interior surface 400 of the chamber body 102 and the bracket 205. The contact pads 236 of the side grounding devices 112 are adapted to contact the ledges 124 (four are shown in phantom) that are electrically coupled to the interior surface 400 of the chamber body 102 to provide a RF return path for the applied RF power. While not shown, bottom grounding devices 113 are also coupled to the susceptor 104.

[0046] In one embodiment, the spacing and concentration of the side grounding devices 112 and/or the bottom grounding devices 113 are configured to provide symmetry in the RF return path to facilitate plasma uniformity and enhanced deposition uniformity on the substrate 101. In one embodiment, the spacing and concentration of the side grounding devices 112 and/or the bottom grounding devices 113 is adapted to provide a symmetrical appearance to the applied RF power to account for variances in the chamber construction, such as the presence of a slit valve opening 405 on one side of the chamber body 102. The spacing or concentration of the side grounding devices 112 and/or the bottom grounding devices 113 allows the applied RF power to travel symmetrically in the processing volume when the chamber may not be physically and/or electrically symmetrical.

[0047] As shown in Figure 4, the susceptor 104 includes the perimeter 200 which includes two major sides 410 and two minor sides 415. The major sides 410 oppose each other and are adjacent to the minor sides 415, which also oppose each other. The susceptor 104 includes an electrical grounding portion or length 420 on each of the major sides 410 and the minor sides 415. The electrical grounding length 420 is less than a length of the respective major sides 410 and minor sides 415 of the susceptor 104. It is within the electrical grounding length 420 where each of the side grounding devices 112 and/or the bottom grounding devices 113 are positioned. The perimeter 200 also includes corners 425 where each of the major sides 410 and minor sides 415 meet. In some embodiments, the side grounding devices 112 and/or the bottom grounding devices 113 are not positioned on the corners 425.

[0048] The positioning of the side grounding devices 112 and the bottom grounding devices 113 as described herein was tested extensively to determine RF grounding efficacy of a plasma system, such as the plasma processing system 100 discussed above. Factors of concern included arcing potential between the susceptor 104 and grounded portions of the system where arcing could potentially damage the system and/or the substrate, as well as devices formed on the substrate. Thus, it is not obvious to arbitrarily remove grounding devices from, and/or re-position grounding devices on, plasma system components, as arcing will damage these components. In particular, removing grounding devices from corners of the susceptor 104 is not obvious, as these areas possess a high potential for arcing. [0049] Figures 5A-5C are schematic isometric views of various embodiments of grounding devices disposed on the bracket 205 on the perimeter 200 of a susceptor 104 (not shown for clarity). In each of the embodiments shown, the side grounding devices 112 and the bottom grounding devices 113 are not positioned at corners 425.

[0050] In Figure 5A there are eight side grounding devices 112 on the major sides 410 of the susceptor 104 and six side grounding devices 112 on the minor sides 415 of the susceptor 104. Flowever, there are eight bottom grounding devices 113 on both of the major sides 410 and the minor sides 415 of the susceptor 104. In the embodiment of Figure 5A, there are two empty base members 300 adjacent to the corners 425.

[0051] In Figure 5B there are four side grounding devices 112 on the major sides 410 of the susceptor 104 and four side grounding devices 112 on the minor sides 415 of the susceptor 104. Flowever, there are eight bottom grounding devices 113 on both of the major sides 410 and the minor sides 415 of the susceptor 104. In the embodiment of Figure 5B, there are two empty base members 300 on the major sides 410 adjacent to the corners 425 while the minor sides 415 include one empty base member 300 adjacent to the corners 425.

[0052] In Figure 5C there are six side grounding devices 112 on the major sides 410 of the susceptor 104 and six side grounding devices 112 on the minor sides 415 of the susceptor 104. Flowever, similar to other embodiments, there are eight bottom grounding devices 113 on both of the major sides 410 and the minor sides 415 of the susceptor 104. In the embodiment of Figure 5C, similar to Figure 5B, there are two empty base members 300 on the major sides 410 adjacent to the corners 425 while the minor sides 415 include one empty base member 300 adjacent to the corners 425.

[0053] The locations and/or spacing between the grounding devices shown in Figures 5A-5C are not exclusive. Flowever, embodiments of the susceptor 104 having the grounding devices coupled thereto as disclosed herein provide more uniform RF distribution on a substrate. Testing of the embodiments of the susceptor 104 described herein show an increase in film uniformity across a substrate. In particular, uniformity at corners of the substrate is significantly improved over conventional susceptor grounding schemes. Embodiments of the susceptor 104 as described herein also improved delta stress of the films formed on a substrate. For example, delta stress decreased from 136 mega Pascals (MPa) to about 5 MPa (at 250 hours aging) using embodiments of the susceptor 104 as described herein. Embodiments of the susceptor 104 as described herein also improved moisture barrier performance of films. Stress stability of the films in high temperature and high humidity environment (e.g., about 85 degrees C at 85% relative humidity) is a critical factor to qualify the moisture barrier performance of the films formed on the substrate. Testing in this high temperature/high humidity environment showed a decrease in delta stress (after 1000 hours aging) from 144 MPa to about 13 MPa using embodiments of the susceptor 104 as described herein. Thus, using the susceptor 104 as described herein, film quality at corners of the substrate sufficiently protects the film from oxidation after 1000 hours aging in high temperature and high humidity environments.

[0054] 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.