Multi-section plasma confinement ring structure

Abstract

A confinement ring for use in a plasma processing chamber includes an upper horizontal section, an upper vertical section, a middle section, a lower vertical section, a lower horizontal section, and a vertical extension. The upper horizontal section extends between an inner upper radius and a first outer radius of the confinement ring. The middle section extends between an inner upper radius and a second outer radius of the confinement ring. The lower horizontal section extends between an inner lower radius and a second outer radius, and the vertical extension extends downwardly from the lower horizontal section proximate the inner lower radius. The upper vertical section extends between the upper horizontal section and the middle section proximate the inner upper radius, and the lower vertical section extends between the middle section and the lower horizontal section proximate the second outer radius.

Description

[Technical field]

[0001] The present invention relates to confinement ring designs used in semiconductor processing modules. [Background technology]

[0002] In semiconductor processing, a substrate undergoes various operations to form features that define an integrated circuit. For example, in a deposition operation, the substrate is received in a processing chamber and, depending on the type of feature to be formed, a specific type of reactive gas is supplied to the chamber and radio frequency power is applied to generate a plasma. The substrate is received on a substrate support defined on a lower electrode, such as an electrostatic chuck. An upper electrode, such as a showerhead, is used to supply a specific type of reactive gas into the process chamber. Radio frequency power is applied to the reactive gas through a corresponding matching network to generate a plasma that is used to selectively deposit ions onto the surface of the substrate to form the microscopic features. The reactive gas generates by-products, such as particulates, gases, etc., that must be quickly removed from the plasma chamber to maintain the integrity of the microscopic features formed on the surface of the substrate.

[0003] To confine the plasma generated within the process region, a set of confinement rings is defined to surround the process region. Furthermore, to improve yield and ensure that the majority of the plasma resides above the substrate received for processing, the confinement rings surrounding the plasma region may be designed to extend the process region to cover not only the region above the substrate, but also the region above an edge ring disposed to surround the substrate when received for processing, and the region above an outer confinement ring disposed adjacent to the edge ring. The set of confinement rings not only act to confine the plasma within the process region, but also act to protect the internal structure of the processing chamber, including the chamber walls. The set of confinement rings is generally a C-shaped structure (i.e., a C-shroud).

[0004] The integrity of features formed on the surface of the substrate depends on a uniform plasma density in the process region. Plasma uniformity can be adjusted by adjusting the shape of a set of confinement rings (e.g., a C-shroud) and increasing the volume of the process region. Any changes to the shape or design of the confinement rings must be made such that the changes do not compromise the mechanical strength or shorten the life of the confinement rings. Furthermore, it would be advantageous if changes to the shape or design of the confinement rings did not require changes to the hardware used within the process chamber, such as the processing chamber's spacer plates, mating hardware, etc.

[0005] It is in this context that embodiments of the present invention arise. Summary of the Invention

[0006] Various embodiments of the present invention define a design of a confinement ring used in a plasma processing chamber to confine plasma within a plasma region. The confinement ring is coupled to an upper electrode structure disposed at a top portion of the plasma processing chamber and is designed to have an S-shaped structure. The S-shaped confinement ring is defined to include an upper horizontal section, an upper vertical section, a middle section, a lower vertical section, a lower horizontal section, and a vertical extension, according to some embodiments. The upper horizontal section is defined to extend between a first outer radius and an inner upper radius. The middle section is defined to extend between an inner upper radius and a second outer radius. The lower horizontal section is defined to extend between a second outer radius and an inner lower radius. The upper vertical section is defined to extend between the upper horizontal section and the middle section at the inner upper radius, and the lower vertical section is defined to extend between the middle section and the lower horizontal section at the second outer radius. The vertical extension is defined to extend downwardly from the lower horizontal section at the inner lower radius.

[0007] The S-shaped structure of the confinement rings helps improve the radial plasma density uniformity while keeping the gas conductance the same as that of conventional confinement rings (i.e., C-shaped confinement rings). In addition, the S-shape helps reduce the volume of plasma in the plasma region while improving the radial etching uniformity of the substrate. Additional design configurations including a slope at the bottom surface of the middle section, and / or a slope at the top surface of the lower horizontal section, and / or a sloped lower horizontal section, etc., may also be considered to improve the radial plasma density uniformity, reduce the volume, and improve the etching uniformity. The S-shaped structure helps regulate the plasma density uniformity in the plasma region without requiring redesign of other hardware components of the plasma processing chamber. In addition, the S-shaped design of the confinement rings protects the mechanical strength and maintains or improves the life of the consumable confinement rings.

[0008] The lower horizontal section includes a plurality of slots (also referred to as "conductance slots") defined along the length of the lower horizontal section to remove by-products and neutral gas species generated within the plasma region. The plurality of slots is designed to ensure optimal confinement of the plasma within the plasma region. Each slot is defined to extend radially from an inner diameter to an outer diameter along the lower horizontal section and vertically between a top surface and a bottom surface of the lower horizontal section. In some implementations, each slot of the plurality of slots is defined to include a parallel slot geometry, where an inner slot radius defined at the inner diameter is equal to an outer slot radius defined at the outer diameter. In an alternative implementation, each slot of the plurality of slots is defined using a tapered slot geometry, where an inner slot radius defined at the inner diameter is smaller than an outer slot radius defined at the outer diameter.

[0009] The tapered slot geometry is designed to address the differential wear that occurs along the length of the slot due to continued exposure to plasma. Typically, the wear of the slot is greater at the inner diameter than at the outer diameter. This uneven wear may be due to differences in the volume of plasma near the inner diameter of the slot as opposed to the outer diameter. When the wear reaches a critical dimension, the confinement rings must be replaced quickly to prevent plasma deconfinement events from occurring. The tapered slot geometry efficiently utilizes the area around the slot by defining a narrow end at the inner diameter, thereby providing more area for wear and less area for wear at the wider end at the outer diameter. This tapered geometry causes the narrow end to experience greater wear, such that the wear at the narrow end of the slot approaches the critical dimension at approximately the same time as the wider end of the slot, resulting in the entire length of the slot reaching the critical confinement dimension at the end of its life. The tapered slot geometry efficiently manages the limited space between the slots, thereby extending the useful life of the confinement rings while maintaining optimal plasma confinement within the plasma region. As a result, the costs associated with the consumable confinement rings decrease as the number of process cycles the confinement rings can be used in the plasma processing chamber increases. The S-shaped structure of the confinement rings provides the added benefit of improving plasma density uniformity in a smaller volume and does not require redesign of other hardware components of the plasma processing chamber.

[0010] In one embodiment, a confinement ring for use in a plasma processing chamber is disclosed. The confinement ring includes an upper horizontal section, an upper vertical section, a middle section, a lower vertical section, a lower horizontal section, and a vertical extension. The upper horizontal section extends between an inner upper radius and a first outer radius. The middle section extends between an inner upper radius and a second outer radius. The lower horizontal section extends between an inner lower radius and a second outer radius of the confinement ring. The upper vertical section extends between the upper horizontal section and the middle section proximate the inner upper radius. The lower vertical section extends between the middle section and the lower horizontal section proximate the second outer radius. The vertical extension extends downwardly proximate the inner lower radius.

[0011] In one embodiment, a plasma volume is disposed between an upper electrode structure, a lower electrode, and confinement rings.

[0012] In one embodiment, an exterior volume is defined between the upper horizontal section, the upper vertical section, and the middle section. The exterior volume is outside the plasma volume.

[0013] In one embodiment, an interior volume is defined between the middle section, the lower vertical section, and the lower horizontal section. The interior volume is inside the plasma volume.

[0014] In one embodiment, an exterior volume is defined between the upper electrode structure, the upper vertical section, and the middle section, and an interior volume is defined between the middle section, the lower vertical section, and the lower horizontal section. The interior volume is inside a plasma volume of the plasma processing chamber, and the exterior volume is outside the plasma volume. The exterior volume reduces the plasma volume.

[0015] In one embodiment, the upper horizontal section, the upper vertical section, the middle section, the lower vertical section, and the lower horizontal section together define an S-shaped structure.

[0016] In one embodiment, the length of the middle section and the length of the lower horizontal section are of uniform thickness.

[0017] In one embodiment, a top surface of the mid-section includes a flat profile and a bottom surface of the mid-section is angled downwardly from the inner upper radius toward the second outer radius, such that a first thickness of the mid-section proximate the inner upper radius is less than a second thickness of the mid-section proximate the second outer radius.

[0018] In one embodiment, a first height defined between a top surface of the lower horizontal section and a bottom surface of the middle section proximate the second outer radius is less than a second height defined between a top surface of the middle section and a bottom surface of the upper horizontal section proximate the inner upper radius.

[0019] In one embodiment, a first height defined between the top surface of the lower horizontal section and the bottom surface of the middle section proximate the second outer radius is equal to a second height defined between the top surface of the middle section and the bottom surface of the upper horizontal section proximate the inner upper radius, and a third height defined between the top surface of the lower horizontal section and the bottom surface of the middle section proximate the inner upper radius.

[0020] In one embodiment, the second outer radius extends beyond the first outer radius, the second outer radius defines an outer radius of the confinement ring, and the inner upper radius is greater than the inner lower radius.

[0021] In one embodiment, the lower horizontal section includes a plurality of slots, each of which extends radially from an inner diameter to an outer diameter along the lower horizontal section, the inner diameter of the slot being greater than an inner ring diameter of the confinement ring defined by an inner lower radius, and the outer diameter of the slot being less than an outer ring diameter of the confinement ring defined by a second outer radius, and each slot extending from a top surface to a bottom surface of the lower horizontal section.

[0022] In one embodiment, the inner slot radius of each slot at the inner diameter is less than the outer slot radius of each slot at the outer diameter. The difference in the inner and outer slot radii of each slot defines a slot taper. Each slot tapers downward from the outer diameter to the inner diameter. The inner and outer slot radii, which affect the slot taper, are defined to be the inverse of the wear rates at the corresponding inner and outer diameters of the slot.

[0023] In one embodiment, the ratio of the inner slot radius to the outer slot radius is from about 1:1.1 to about 1:1.5.

[0024] In one embodiment, the inner slot radius of each slot at the inner diameter is equal to the outer slot radius of each slot at the outer diameter.

[0025] In one embodiment, the first height of the first vertical section is equal to the second height of the second vertical section.

[0026] In one embodiment, the first height of the first vertical section is different from the second height of the second vertical section.

[0027] In one embodiment, the upper horizontal section, the upper vertical section, the middle section, the lower vertical section, and the lower horizontal section form a unitary S-shaped structure, with the vertical extension continuing integrally downwardly with the S-shaped structure proximate the inner lower radius, The unitary S-shaped structure is configured to confine a plasma within a plasma region defined in the plasma processing chamber.

[0028] In one embodiment, the upper horizontal section, the upper vertical section, the middle section, and the lower vertical section define a first unitary piece and the lower horizontal section defines a second piece, the first unitary piece configured to be received over a radio frequency gasket defined on a top surface proximate the second outer radius of the second piece.

[0029] In one embodiment, the lower horizontal section includes a slope extending downwardly from the lower vertical section toward the inner lower radius. The thickness along the length of the lower horizontal section is uniform.

[0030] In one embodiment, the lower vertical section includes one or more optical emission spectroscopy holes in which probes are positioned to monitor the plasma within the plasma processing chamber for endpoint detection.

[0031] In one embodiment, a top surface of the upper horizontal section includes a plurality of holes configured to receive cam keys for coupling the confinement ring to corresponding cam locks disposed on a bottom surface of a backing plate disposed in the plasma processing chamber, each cam key of the plurality of cam keys being positioned to align with a corresponding cam lock of the plurality of cam locks.

[0032] In one embodiment, the vertical extension is defined by an angled top section and a vertical bottom section, the angled top section being defined outwardly adjacent the top surface of the lower horizontal section at an inner lower radius, and the vertical bottom section being defined extending downwardly from a bottom portion of the angled top section at an inner lower radius.

[0033] In an alternative embodiment, a confinement ring for use in a plasma processing chamber is disclosed. The confinement ring includes an upper horizontal section, an upper vertical section, a middle section, a lower vertical section, a lower horizontal section, and a vertical extension. The upper horizontal section extends between an inner upper radius and a first outer radius. The middle section extends between an inner upper radius and a second outer radius and includes a top surface having a flat profile and a bottom surface including a slope extending downwardly from the inner upper radius to the second outer radius. The lower horizontal section extends between an inner lower radius and a second outer radius of the confinement ring. The upper vertical section extends between the upper horizontal section and the middle section proximate the inner upper radius. The lower vertical section extends between the middle section and the lower horizontal section proximate the second outer radius. A vertical extension extends downwardly from the lower horizontal section proximate the inner lower radius.

[0034] In one embodiment, the top surface of the lower horizontal section is defined by a first slope extending downwardly from the lower vertical section toward the inner lower radius.

[0035] In one embodiment, a first height defined between a bottom surface of the middle section and a top surface of the lower horizontal section proximate the second outer radius is less than a second height defined between a bottom surface of the middle section and a top surface of the lower horizontal section proximate the inner lower radius.

[0036] In one embodiment, a bottom surface of the lower horizontal section is defined to include a flat profile such that a first slope of the lower horizontal section defines a variable thickness along a length of the lower horizontal section, the variable thickness being defined by a first thickness proximate the second outer radius and a second thickness proximate the inner lower radius, the first thickness being greater than the second thickness.

[0037] In one embodiment, the bottom surface of the lower horizontal section is defined by a second slope extending downwardly from the lower vertical section toward the inner lower radius, the first slope angle of the first slope being equal to the second slope angle of the second slope, such that the thickness along the length of the lower horizontal section is uniform.

[0038] In one embodiment, the upper horizontal section, the upper vertical section, the middle section, the lower vertical section, and the lower horizontal section together form a unitary S-shaped structure. A vertical extension continues downwardly with the S-shaped structure proximate the inner lower radius.

[0039] In one embodiment, the upper horizontal section, the upper vertical section, the middle section, and the lower vertical section define a first unitary piece and the lower horizontal section defines a second piece, the first unitary piece configured to be received over a radio frequency gasket defined on a top surface disposed proximate to a second outer radius of the second piece.

[0040] In one embodiment, the lower horizontal section includes a plurality of slots. Each slot extends radially from an inner diameter to an outer diameter along the lower horizontal section. The inner diameter of the slot is greater than an inner ring diameter of the confinement ring defined by an inner lower radius, and the outer diameter of the slot is less than an outer ring diameter of the confinement ring defined by a second outer radius. Each slot extends from a top surface to a bottom surface of the lower horizontal section.

[0041] In yet another alternative embodiment, a plasma processing chamber for confining a plasma therein is disclosed. The plasma processing chamber includes a lower electrode, an upper electrode structure, and a confinement ring disposed between the lower electrode and the upper electrode structure. The lower electrode is disposed in a lower section (i.e., a lower portion) of the plasma processing chamber and includes a support surface for supporting a substrate. The upper electrode structure is disposed in an upper section (i.e., an upper portion) of the plasma processing chamber and faces opposite the lower electrode. The confinement ring is coupled to the upper electrode structure and disposed between the lower electrode and the upper electrode structure. The confinement ring includes an upper horizontal section, an upper vertical section, a middle section, a lower vertical section, a lower horizontal section, and a vertical extension. The upper horizontal section extends between an inner upper radius and a first outer radius. The middle section extends between an inner upper radius and a second outer radius. The lower horizontal section extends between an inner lower radius and a second outer radius of the confinement ring. The upper vertical section extends between the upper horizontal section and a middle section proximate to the inner upper radius. The lower vertical section extends between the intermediate section and the lower horizontal section proximate the second outer radius. A vertical extension extends downwardly from the lower horizontal section proximate the inner lower radius.

[0042] In one embodiment, the plasma volume is disposed between an upper electrode, a lower electrode, and confinement rings.

[0043] In one embodiment, the upper electrode structure includes an outer electrode disposed at a center of the upper electrode structure and an outer electrode disposed adjacent to the upper electrode, and the backing plate is disposed to surround the outer electrode. The backing plate includes an outer portion disposed adjacent to the outer electrode such that the outer electrode is disposed between the upper electrode and the outer portion of the backing plate, and an inner portion disposed over a portion of the outer electrode. A bottom surface of the outer portion of the backing plate includes a plurality of cam locks that align with corresponding keys disposed on a top surface of the upper horizontal section of the confinement ring. The cam keys and cam locks are used to couple the outer electrode to the confinement ring.

[0044] In one embodiment, the plurality of cam keys are coupled to a controller configured to generate a first signal that actuates the plurality of cam keys to engage and lock the plurality of cam locks during coupling to the backing plate and a second signal that actuates the plurality of cam keys to allow unlocking of the plurality of cam locks during decoupling of the confinement ring from the backing plate. The plurality of cam locks and the plurality of cam keys are part of an electronic cam lock mechanism used to couple the confinement ring to the upper electrode structure and are configured to be controlled by signals from the controller.

[0045] In one embodiment, the backing plate and the upper electrode of the upper electrode structure are electrically grounded, and the lower electrode is coupled to a radio frequency (RF) generator through a corresponding matching network, the RF generator being configured to provide RF power to the lower electrode to generate a plasma in the plasma processing chamber. [Brief description of the drawings]

[0046] [Figure 1] FIG. 1 is a cross-sectional view of a portion of a plasma processing chamber in which confinement rings are used, according to one embodiment.

[0047] [Figure 2A] FIG. 2A is an expanded view of an exemplary S-shaped confinement ring disposed between an upper electrode structure and a lower electrode, according to one embodiment.

[0048] [Figure 2B] FIG. 2B illustrates an alternative embodiment of a plasma processing chamber including an S-shaped confinement ring disposed between the upper electrode structure of FIG. 2A and a lower electrode, the alternative embodiment including a modified upper electrode structure.

[0049] [Figure 3A]FIG. 3A is a perspective view of the top of an S-shaped confinement ring used in a plasma processing chamber to confine a plasma, according to one embodiment.

[0050] [Figure 3B] FIG. 3B is a perspective view of the bottom of an S-shaped confinement ring, according to one embodiment.

[0051] [Figure 4] FIG. 4 is a top view of an S-shaped confinement ring illustrating some features according to one embodiment.

[0052] [Diagram 5] FIG. 5 is a vertical cross-sectional view (cross-sectional view representing section AA of FIG. 4) of an S-shaped confinement ring illustrating additional features, according to one embodiment.

[0053] [Figure 6A] FIG. 6A is an expanded cross-sectional view of a unitary S-shaped confinement ring showing a slot in the lower horizontal section, according to one embodiment.

[0054] [Figure 6B] FIG. 6B illustrates an alternative embodiment of the S-shaped confinement ring shown in FIG. 6A, where the S-shaped confinement ring is made in two pieces.

[0055] [Figure 6C] FIG. 6C is an expanded view of section CC of FIG. 6A according to an alternative embodiment of the present disclosure, in which the S-shaped confinement ring includes a different profile of the middle section.

[0056] [Figure 6D] FIG. 6D is an expanded view of section CC of FIG. 6A according to another alternative embodiment of the present disclosure, in which the S-shaped confinement ring includes different profiles for the middle section and the lower horizontal section.

[0057] [Figure 7]FIG. 7 is a top view of a bottom portion of an S-shaped confinement ring having multiple slots (ie, conductance slots) according to one embodiment.

[0058] [Figure 8A] FIG. 8A is an expanded view of section H of the S-shaped confinement ring identified in FIG. 7, according to one embodiment.

[0059] [Figure 8B] FIG. 8B is a close-up view of slots contained in section H of the lower horizontal section of the S-shaped confinement ring, where the slots are defined by parallel slot profiles, according to one embodiment.

[0060] [Figure 8C] FIG. 8C is a close-up view of a slot included in section H of the lower horizontal section of the S-shaped confinement ring according to an alternative embodiment, where the slot is defined by a tapered slot profile.

[0061] [Figure 8D] FIG. 8D is a close-up view of a slot included in section H of the lower horizontal section of the S-shaped confinement ring according to another alternative embodiment, where the slot is defined by a curved slot profile. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] In various embodiments described herein, confinement rings for use in plasma processing chambers are designed to maintain plasma uniformity in the plasma region. The confinement rings are designed to have an S-shaped configuration. The S-shape reduces the volume in the plasma region in which the plasma is contained, reducing the amount of RF power required to generate the plasma to fill the plasma region. The reduced plasma volume improves radial plasma density uniformity in the plasma region, thereby improving radial etching uniformity of the substrate. Furthermore, the S-shaped design of the confinement rings can be used in the plasma processing chamber with the current configuration of other hardware components, without requiring redesign of the other hardware components. In some embodiments, the hardware components may be redesigned to further reduce the volume of plasma maintained in the plasma region, although this is not required.

[0063] A number of slots (i.e., conductance slots) are provided at the bottom of the S-shaped confinement ring, which efficiently removes by-products from the plasma region while optimally confining the plasma within the plasma region, resulting in improved gas conductance. The slots can be shaped to have a parallel slot profile or a tapered slot profile. A tapered slot design can be used to address differential wear along the length of the slot and efficiently utilize the area around the slot. The tapered slot profile improves the useful life of the confinement ring by ensuring optimal use of the limited space between the slots. As a result, the cost associated with replacing the consumable confinement ring decreases as the number of process cycles the confinement ring can be used in the plasma processing chamber increases. Thus, the S-shaped design of the confinement ring improves density and gas conductance while maintaining plasma uniformity in a smaller volume.

[0064] The S-shaped confinement ring for use in a plasma processing chamber includes an upper horizontal section, an upper vertical section, a middle section, a lower vertical section, and a lower horizontal section. The lower horizontal section further includes a vertical extension used to mount the confinement ring on top of an RF gasket defined in a portion of the lower electrode. The upper horizontal section extends between a first outer radius and an inner upper radius. The middle section extends between an inner upper radius and a second outer radius. The lower horizontal section extends between an inner lower radius and a second outer radius. The upper vertical section extends between the upper horizontal section and the middle section adjacent the inner upper radius, and the lower vertical section extends between the middle section and the lower horizontal section adjacent the second outer radius. The vertical extension extends downward adjacent the inner lower radius and is integrally continuous with the lower horizontal section. The upper horizontal section, the upper vertical section, the middle section, the lower vertical section, and the lower horizontal section together form an S-shaped structure that is used to effectively confine the plasma generated in the plasma processing chamber while reducing the amount of plasma contained in the plasma region.

[0065] Variations in the profile of the middle section, and in some implementations, the lower horizontal section, may also be envisioned, with the variations affecting the amount of plasma contained in the plasma region and the density of the plasma. Similar to conventional C-shaped confinement rings, the S-shaped confinement ring structure improves the uniformity of the plasma density within the plasma region defined in the plasma processing chamber. The variation in the profile of the middle section may be in the form of a slope along the bottom surface of the middle section, the slope extending downward from the inner top radius to the second outer radius. The slope in the middle section creates a variation in thickness along the length of the middle section, with the thickness adjacent the inner top radius being less than the thickness adjacent the second outer radius. Similarly, the variation in the profile of the lower horizontal section may be in the form of a slope defined on the top surface of the lower horizontal section, the slope in the lower horizontal section extending downward from the second outer radius to the inner bottom radius. An additional slope may be defined on the bottom surface of the lower horizontal section to make the thickness of the lower horizontal section uniform along the length of the lower horizontal section.

[0066] The slope in the middle section reduces the plasma volume in the plasma region. The reduction in plasma volume reduces the amount of gas required to form the plasma to fill the plasma region. Even with the reduced volume, the S-shaped confinement ring ensures uniformity of the plasma density in the plasma region as well as improved uniformity of substrate etching. Furthermore, the S-shaped structure does not compromise the mechanical strength of the confinement ring, thereby maintaining the useful life of the confinement ring. These advantages are realized without the need to modify hardware components (e.g., chamber spacer plates, mating hardware, etc.) in the plasma processing chamber, since the changes made to the confinement ring structure do not substantially deviate from the overall structure of conventional confinement rings.

[0067] Given the foregoing summary of the invention, specific embodiments will now be described with reference to the various figures.

[0068] FIG. 1 shows a simplified block diagram of a portion of a plasma processing chamber 100 that uses S-shaped confinement rings to confine plasma in one embodiment. The plasma processing chamber 100, which may be a capacitively coupled plasma (CCP) processing chamber (or simply referred to hereinafter as "plasma processing chamber") in one embodiment, includes a lower electrode 104 that supplies radio frequency (RF) power to the plasma processing chamber 100 and an upper electrode structure 102 that supplies process gas to generate plasma in the plasma processing chamber 100. The upper electrode structure 102 is defined in an upper chamber portion 100a of the plasma processing chamber 100, and the lower electrode 104 is defined in a lower chamber portion 100b of the plasma processing chamber 100. The lower electrode 104 is connected to an RF power source 106 through a corresponding matching network 107, a first end of the RF power source 106 is connected to the matching network 107, and a second end of the RF power source 106 is electrically grounded. The RF power source 106 may include one or more RF power generators (not shown).

[0069] In one embodiment, the top surface of the lower electrode (e.g., electrostatic chuck (ESC)) 104 defines a substrate support surface on which a substrate 110 (e.g., a wafer) is received for processing. In some embodiments, the substrate support surface is defined in a recess defined in the top surface of the lower electrode, the height of the recess being equal to the thickness of the substrate 110. An edge ring 112 is defined adjacent to the substrate support surface of the lower electrode 104 to surround the substrate 110 when it is received for processing. It should be noted that throughout this application, a substrate may be interchangeably referred to as a wafer and refers to a thin slice of semiconductor material (mostly made of silicon) that acts as a base on which multiple fabrication operations are performed to fabricate electronic integrated circuits, at least one of which employs a plasma generated in a plasma processing chamber in which an S-shaped confinement ring is used. In some implementations, the edge ring 112 is designed such that a top surface of the edge ring 112 is flush with a top surface of the substrate 110 when the substrate 110 is supported on the substrate support surface of the lower electrode 104. The edge ring 112 is configured to extend a processing region for the plasma generated in the plasma processing chamber 100 (represented by the plasma region 108) over an area beyond the edge of the substrate, covering the outer edge of the edge ring 112 and extending beyond the extended processing region. A cover ring 114 is disposed adjacent to the edge ring 112 such that the edge ring 112 is disposed between the cover ring 114 and the substrate 110 when the substrate is received on the substrate support surface. In some implementations, the cover ring 114 is designed such that a top surface of the cover ring 114 is flush with a top surface of the edge ring 112 to further extend the processing region from the outer edge of the edge ring 112 to the outer edge of the cover ring 114. An RF power supply 106 is connected to the bottom portion of the lower electrode through a matching network 107 to supply RF power to the plasma processing chamber 100 .

[0070] One or more insulating elements 120 are disposed adjacent to and surrounding the lower electrode 104 under the cover ring 114. In one embodiment, the insulating elements 120 can be made of a quartz material and are therefore also referred to as quartz elements, although other insulating materials can be used. A ground ring 122 is disposed adjacent to the insulating elements (e.g., quartz elements) 120 and below the cover ring 114 such that the ground ring 122 surrounds the quartz elements 120 and the lower electrode 104. A support structure in the form of a ground bucket 124 is disposed on the lower electrode 104 surrounding a portion of the ground ring 122. In one embodiment, a gap exists between the ground ring 122 and the ground bucket 124 to provide a capacitive coupling to the ground ring 122. The ground bucket 124 provides a ground return for the RF power supplied to the plasma processing chamber 100. The ground bucket 124 also provides sufficient support for a portion of the upper electrode structure 102 to rest thereon. For example, a bottom portion of the S-shaped structure of the confinement ring 130 coupled to a portion of the upper electrode structure 102 rests on the grounded bucket 124. In this case, the grounded bucket 124 provides indirect support to the upper electrode structure 102 via the S-shaped confinement ring structure 130. The grounded bucket 124, in one embodiment, includes a fixed ring 124a at the bottom and a floating element 124b at the top. A flexible RF strap 125 is defined between the fixed ring 124a and the floating element 124b. An RF gasket 116 is disposed on the top surface of the floating element 124b of the grounded bucket 124. The components of the grounded bucket 124 (i.e., the fixed ring 124a, the floating element 124b, and the flexible RF strap 125) are made of aluminum in one embodiment. In other embodiments, the components of the grounded bucket 124 are made of any other conductive material suitable for conducting RF power to ground in the plasma processing chamber 100. In some implementations, the RF gasket 116 may be disposed within a channel defined in the top surface of the floating element 124b.

[0071] In one embodiment, the upper electrode structure 102 may include a centrally located upper electrode 102a and an outer electrode 102b disposed adjacent to and surrounding the upper electrode 102a. The upper electrode 102a may be a showerhead including one or more inlets (not shown) connected to one or more process gas sources (not shown) and multiple outlets (not shown) distributed on a bottom surface of the upper electrode 102a facing the lower electrode 104. The multiple outlets are configured to deliver process gas from the one or more process gas sources to a plasma processing region (or simply referred to as a "plasma region") 108 defined between the upper electrode 102a and the lower electrode 104. The upper electrode 102a is electrically grounded in this embodiment and provides a return path to ground for the RF power supplied to the plasma processing chamber 100. In one embodiment shown in FIG. 1, the upper electrode 102a includes an extension defined on its top surface at an outer radius. This extension is used to mate the top electrode 102a with a corresponding lip defined on the bottom surface at the inner radius of the outer electrode 102b. In addition to the top electrode 102a and the outer electrode 102b, the top electrode structure 102 includes a backing plate 105. The backing plate 105 includes an outer portion 105a surrounding the outer electrode 102b and an inner portion 105b disposed on and covering at least a portion of the top surface of the outer electrode 102b. The outer electrode 102b includes a plurality of fastening means (not shown) disposed on the portion of the top surface covered by the inner portion 105b of the backing plate 105 for coupling the outer electrode 102b to the backing plate 105. A plurality of locking mechanisms, such as cam locks (not shown), are uniformly distributed along the bottom surface of the outer portion 105a of the backing plate 105 surrounding the outer electrode 102b. Each cam lock is designed to align with a corresponding cam key located on the top surface of the containment ring structure 130 located below the backing plate 105, allowing the containment ring structure 130 to be coupled to the backing plate 105.

[0072] In one embodiment, the upper electrode structure 102 with the confinement ring structure 130 coupled thereto is configured to move vertically up and down while the lower electrode 104 is fixed. When the plasma processing chamber 100 is prepared for processing, the upper electrode structure 102 with the confinement ring structure 130 is lowered to allow the confinement ring structure 130 to rest on the RF gasket 116 disposed on the top surface of the floating element 124b of the grounded bucket 124. The confinement ring structure 130 presses down on the RF gasket 116, compressing it and forming a tight bond between the upper electrode structure 102 and the lower electrode 104. The compression of the RF gasket 116 presses down on the floating element 124b, thereby compressing the flexible RF straps 125. As the upper electrode structure 102 moves upward, the confinement ring structure 130 moves upward and away from the RF gasket 116, allowing the RF gasket 116 to relax. This causes the floating element 124b and the flexible RF straps 125 to move from a compressed state to a relaxed state.

[0073] A confinement ring structure (or simply referred to as a "confinement ring") 130 coupled to the backing plate 105 serves as a bonding interface between the upper electrode structure 102 and the lower electrode 104. The confinement ring 130 defines a confined plasma volume between the upper electrode structure and the lower electrode (102, 104) in which the plasma generated in the chamber is sufficiently confined. The plasma volume defines the plasma region 108. The confinement ring 130 is an S-shaped structure with an opening at the lower part of the S-shape facing the inside of the plasma region 108. FIG. 1 shows an example of a left portion of a plasma processing chamber having an S-shaped confinement ring structure with an opening at the lower part of the inverted S-shaped confinement ring 130 facing the inside of the plasma region 108, which extends across the surfaces of the substrate 110, edge ring 112, and cover ring 114 disposed on the lower electrode 104 of the plasma processing chamber 100. A number of keys of a locking mechanism, such as cam keys, are defined on the top surface of the confinement ring 130. The cam keys are configured to mate with corresponding cam locks disposed on a bottom surface of the outer portion 105a of the backing plate 105. The confinement ring 130 is part of the upper electrode structure 102, and a bottom section of the confinement ring 130 is configured to rest on an RF gasket 116 defined on a top surface of a grounded bucket 124 defined in the lower electrode 104. The RF gasket 116 ensures that the bond between the upper and lower electrodes 102, 104 is airtight. In one embodiment, the grounded bucket 124 is configured to surround an area of ​​the lower electrode 104 including at least the substrate support 110, the edge ring 112, the cover ring 114, the one or more quartz elements 120, and the grounded ring 122. The grounded bucket 124 provides a return path to ground for RF current provided to the lower electrode 104 by the RF power supply 106.

[0074] It should be noted that while the plasma processing chamber in Figure 1 is shown to include only certain parts described herein, in practice, a plasma processing chamber may include several additional components necessary to process a substrate. For example, a lift pin mechanism having lift pins for raising and lowering the substrate 110 is not shown. Additionally, the various components shown in Figure 1 may not be to scale and / or may be exaggerated to discern different features of the various components.

[0075] The confinement ring 130 is generally defined by a number of components including an upper horizontal section, an upper vertical section, a middle section, a lower vertical section, a lower horizontal section and a vertical extension. A number of cam locks are distributed on the top surface of the upper horizontal section and are used to couple the confinement ring 130 to the outer portion 105a of the backing plate 105 of the upper electrode structure 102, which includes an upper electrode 102a, an outer electrode 102b and a backing plate 105. The upper vertical section of the S-shaped confinement ring 130 acts to reduce the plasma volume in the plasma region 108 for receiving the plasma. The reduction in the plasma volume is achieved without adversely affecting the density or plasma distribution of the plasma in the plasma region 108. Details of the various components of the confinement ring 130 are described in further detail with reference to Figures 2A and 2B.

[0076] FIG. 2A shows an expanded cross-sectional view of a plasma processing chamber 100 in which, in one embodiment, an S-shaped confinement ring 130 is disposed to confine plasma in a plasma region 108. As described with reference to FIG. 1, the plasma processing chamber 100 includes an upper chamber portion 100a in which an upper electrode structure 102 is disposed, and a lower chamber portion 100b in which a lower electrode 104 is disposed. The upper electrode structure 102 includes multiple components including an upper electrode 102a, an outer electrode 102b, and a backing plate 105. The upper electrode 102a is centrally disposed to substantially cover an area above a substrate support surface on which a substrate 110 is received for processing. The outer electrode 102b is disposed adjacent to the upper electrode 102a and surrounding the upper electrode 102a. The outer electrode 102b includes a top surface and a bottom surface. The top surface and the bottom surface of the outer electrode 102b have a flat profile in this embodiment. The outer electrode 102b is electrically grounded. The backing plate 105 includes an outer portion 105a disposed adjacent to and surrounding the outer electrode 102b, and an inner portion 105b disposed over a portion of the outer electrode 102b, the portion of the outer electrode 102b being less than or equal to the entire outer electrode 102b. The backing plate 105 is also electrically grounded.

[0077] In one embodiment, the S-shaped confinement ring 130 is coupled to the outer portion 105a of the backing plate 105 using a fastening mechanism (e.g., a cam lock structure) (not shown). The cam lock structure includes one or more cam locks that can be operated using a corresponding one or more cam keys, for example. In this embodiment, the multiple cam locks (not shown) are evenly distributed across the bottom surface of the outer portion 105a of the backing plate 105. The cam locks can be arranged such that each cam lock aligns with a corresponding cam key (not shown) provided on the top surface of the S-shaped confinement ring 130 that is disposed below the outer portion 105a of the backing plate 105. In one embodiment, the cam lock structure is an electronic cam lock structure, and the cam keys disposed on the top surface of the confinement ring 130 are coupled to a controller and operated using signals from the controller (not shown). The controller can be coupled to the plasma processing chamber 100 and used to control process parameters of the plasma processing chamber 100. For example, the controller may be used to control the process recipe of the process gases used in the plasma processing chamber 100, the RF power supplied to the plasma processing chamber, the exposure time of the substrate 110 to the plasma, the concentration of the gases used in the plasma processing chamber, etc. The controller may be coupled to a computer or may be part of a computer used to provide the process recipe for generating the plasma in the plasma processing chamber 100. In addition to controlling various process parameters, the controller may also be used to provide appropriate signals to the cam keys to lock with the cam locks. For example, in one embodiment, the controller may be used to generate a first signal that actuates the cam keys to engage and lock with the cam locks when the confinement ring 130 needs to be coupled to the outer portion 105a of the backing plate 105. Similarly, the controller may be used to generate a second signal that causes the cam keys to unlock from the cam locks when the confinement ring 130 is to be decoupled from the backing plate 105.In some implementations, a first signal for locking may be generated upon detecting a new confinement ring 130 installed in the plasma processing chamber 100. In some implementations, a second signal for unlocking may be generated when an existing confinement ring 130 needs to be removed, for example, after the confinement ring 130 reaches the end of its useful life. Implementations are not limited to electronic cam lock structures. Instead, other types of cam locks or other types of locking mechanisms (e.g., screws, etc.) can be used to couple the confinement ring 130 to the backing plate 105.

[0078] In the embodiment shown in FIG. 2A, the bottom surface 103b of the outer electrode 102b facing the plasma region 108 is defined to be flat. In one embodiment, the inner side of the outer electrode 102b disposed adjacent to the upper electrode 102a includes a step 109a defined in the top surface. The step 109a can be used to receive a corresponding lip extension 109b defined in the top surface at the outer radius of the upper electrode 102a. The step 109a provides a reliable mating surface for receiving the upper electrode 102a. In addition to the step 109a, the bottom surface at the inner edge of the outer electrode 102b may include a sloped surface 109c in one embodiment. The sloped surface 109c can be designed to allow the plasma to flow unrestrictedly in the plasma region 108. If any part of the plasma region 108 has a sharp edge, the plasma flow may be impeded by the angle of the sharp edge. Therefore, to avoid such impediments to the plasma flow, the inner edge of the bottom surface of the outer electrode 102b is angled downward toward the outer edge of the outer electrode 102b and away from the bottom outer edge of the top electrode 102a. The slope angle of the beveled surface 109c at the inner edge and the length of the beveled surface 109c can be defined to ensure optimal plasma flow in the plasma region 108. In an alternative embodiment, instead of the beveled surface 109c, the inner edge of the bottom surface of the outer electrode 102b may include a rounded edge. Various components of the plasma processing chamber 100 that are common between Figures 1 and 2A are represented using the same reference numbers and perform the same functions.

[0079] In one embodiment, the quartz element 120 in the lower electrode 104 of FIG. 1 may be made of two or more pieces. In the embodiment shown in FIG. 2A, the quartz element 120 includes two quartz elements, namely, quartz element 1 120a, which is disposed adjacent to the ground ring 122 under the cover ring 114, such that a portion of quartz element 1 120a is disposed to surround a first portion of the lower electrode 104 and is between the lower electrode 104 and the ground ring 122. A second quartz element 2 120b is disposed adjacent to a portion of quartz element 1 120a and between a second portion of the lower electrode 104 and quartz element 1 120a. The first portion of the lower electrode 104 is defined above the second portion of the lower electrode 104. Additional quartz elements may be disposed in the lower electrode 104 adjacent to the ground ring 122, the ground bucket 124. The edge ring 112 defined in the bottom electrode 104 may include a step on the inside adjacent the substrate support surface of the bottom electrode 104. The step walls may be defined by straight edges or beveled edges. The step of the edge ring 112 may be defined by a height equal to the thickness of the substrate 110 received on the substrate support surface of the bottom electrode 104, such that when the substrate 110 is received on the substrate support surface, the top surface of the substrate 110 is flush with the top surface of the edge ring 112. Similarly, the thickness of the cover ring 114 may be defined to be equal to the thickness of the edge ring 112 at the outer edge of the edge ring 112, such that the top surface of the cover ring 114 is flush with the top surface of the edge ring 112. The thicknesses of the edge ring 112 and the cover ring 114 are defined based on the substrate support surface of the bottom electrode 104 on which the edge ring and the cover ring are disposed. When the substrate support surface has a different profile, the thicknesses of the edge ring 112 and the cover ring 114 can be defined according to the different profile such that the top surfaces of the edge ring 112 and the cover ring 114 are flush with the top surface of the substrate 110 received thereon. The S-shaped confinement ring 130 is disposed between the upper electrode structure 102 and the lower electrode 104. The upper section 100a of the plasma processing chamber 100, including the upper electrode structure 102 and the confinement ring 130, is capable of vertically moving up and down relative to one another, as indicated by the dashed lines in FIG. 2A.

[0080] The S-shaped confinement ring 130 includes an upper horizontal section 131, an upper vertical section 132, a middle section 133, a lower vertical section 134, and a lower horizontal section 135. A vertical extension 136 extends downward from the lower horizontal section 135 proximate the inner lower radius. The upper horizontal section 131 extends between the inner upper radius and the first outer radius of the confinement ring 130. In one embodiment, the top surface of the upper horizontal section at the inner upper radius includes a step 148 in which a lip extension defined on the outer edge of the bottom surface of the outer electrode 102b is received. The height of the step 148 is defined to provide a reliable mating surface for receiving and supporting the outer electrode 102b. The upper horizontal section 131 is defined by a top surface 131a and a bottom surface 131b. A top surface 131a of the upper horizontal section 131 is defined to be flat and includes a plurality of cam keys (not shown) defined to align with corresponding cam locks (not shown) defined on a bottom surface of the outer portion 105a of the backing plate 105. The cam locks are used to hold the containment ring 130 in place when the containment ring 130 is coupled to the backing plate 105. A bottom surface 131b of the upper horizontal section 131 is defined to be flat such that the thickness along the length of the upper horizontal section 131 is uniform.

[0081] The middle section 133 extends between the inner top radius and the second outer radius of the confinement ring 130. The middle section is also defined by a top surface 133a and a bottom surface 133b. In one embodiment shown in FIG. 2A, the top surface 133a and the bottom surface 133b of the middle section 133 are defined to be flat (i.e., horizontal), such that the thickness "t1" of the middle section 133 proximate the inner top radius is equal to the thickness "t2" of the middle section 133 proximate the second outer radius. The upper vertical section 132 extends between the upper horizontal section 131 and the middle section 133 proximate the inner top radius. In one embodiment, the proximity to the inner top radius is defined to be offset from the junction of the upper vertical section 132 and the middle section 133, the offset being defined by the thickness of the upper vertical section 132. In an alternative embodiment, the proximity to the inner top radius is defined to be between the inner top radius and the outer side (i.e., the side facing away from the plasma region) of the upper vertical section 132. The upper vertical section 132 extends a height "h2". In the embodiment shown in FIG. 2A, the inner side of the upper vertical section 132 facing the plasma region 108 and the outer side of the upper vertical section 132 facing away from the plasma region 108 are defined to be vertical, and the distance between the inner and outer sides of the upper vertical section 132 defines the thickness of the upper vertical section 132. In an alternative embodiment, the inner side of the upper vertical section 132 may include a curved or arcuate profile. In this embodiment, the thickness of the upper vertical section 132 varies along the length of the upper vertical section 132 due to the curved or arcuate profile.

[0082] The lower horizontal section 135 is defined to extend from the inner lower radius to the second outer radius. The lower horizontal section 135 is defined by a top surface 135a and a bottom surface 135b. In the embodiment shown in FIG. 2A, both the top surface 135a and the bottom surface 135b of the lower horizontal section 135 are defined to be flat (i.e., horizontal). In one alternative embodiment, the top surface 135a may include a slope that descends from the second outer radius toward the inner lower radius. In another alternative embodiment, both the top surface 135a and the bottom surface 135b of the lower horizontal section 135 may include a slope that descends from the second outer radius toward the inner lower radius. The slope angles of both the top surface 135a and the bottom surface 135b of the lower horizontal section may be equal in this embodiment. In an alternative embodiment, the slope angle of the top surface 135a may be different from the slope angle of the bottom surface 135b.

[0083] The lower vertical section 134 extends between the middle section 133 and the lower horizontal section 135 proximate the second outer radius. The lower vertical section extends over a height "h1" proximate the second outer radius and a height "h3" proximate the inner upper radius. In the embodiment shown in FIG. 2A, the top and bottom surfaces (133a, 133b) of the middle section 133 are flat (i.e., the thickness t1 of the middle section 133 at the inner upper radius is equal to the thickness t2 at the second outer radius), the top and bottom surfaces (135a, 135b) of the lower horizontal section 135 are flat (i.e., the thickness of the lower horizontal section 135 is uniform along the length of the lower horizontal section 135), and the height h1 proximate the second outer radius is equal to the height h3 proximate the inner upper radius. Further, in one embodiment, the height h1 of the lower vertical section 134 at the second outer radius may be equal to the height h2 of the upper vertical section 132 proximate the inner upper radius. In alternative embodiments, the height h2 may be greater or less than the height h1. The height h2 varies the volume of plasma within the plasma region 108. If a slope is defined on the bottom surface 133b of the middle section 133 and / or if a slope is defined on the top surface 135a of the lower horizontal section 135, the height h1 proximate the second outer radius may be less than the height h3 proximate the inner upper radius.

[0084] The plasma region 108 is defined between the upper electrode structure 102, the lower electrode 104, and the confinement rings 130. The plasma region 108 defines a plasma volume in which plasma generated in the plasma processing chamber 100 is received. The plasma volume in the plasma region 108 includes an outer volume 108a and an inner volume 108b. The outer volume 108a is defined between the upper horizontal section 131, the upper vertical section 132, and the middle section 133. The outer volume 108a is defined in the area directly below the upper electrode 102a and the outer electrode 102b in the plasma region 108 and outside (i.e., at or above) the inner volume 108b. The outer volume 108a reduces the overall volume of plasma in the plasma region 108. In one embodiment, the amount of plasma volume in the plasma region 108 that is reduced by the outer volume 108a is determined by the length of the middle section 133, the height h2 of the upper vertical section 132, and may be determined to some extent by the thickness of the middle section 133. The inner volume 108b is defined between the middle section 133, the lower vertical section 134, and the lower horizontal section 135. The inner volume 108b is defined to be inside the plasma volume and is between the outer volume 108a at the top and the substrate support surface of the lower electrode 104. The amount of plasma that can be contained in the inner volume 108b depends on the length of the middle section 133, the height h1 of the lower vertical section 134, and the length of the lower horizontal section 135.

[0085] The vertical extension 136 is defined to extend downward from the lower horizontal section 135 adjacent the inner lower radius and integrally continue downward with the lower horizontal section 135 for a height. In some implementations, the vertical extension 136 is used in coupling the upper electrode structure 102 to the lower electrode 104. For example, when the plasma processing chamber 100 is prepared for processing, the upper electrode structure 102 is lowered such that the vertical extension 136 of the S-shaped confinement ring 130 rests on the RF gasket 116 disposed on the top surface of the grounded bucket 124 defined in the lower electrode 104. In one implementation, the upper horizontal section 131, the upper vertical section 132, the middle section 133, the lower vertical section 134, and the lower horizontal section 135 together form the integral S-shaped confinement ring 130. The vertical extension 136 defined adjacent the inner lower radius extends the lower horizontal section 135 downward. In an alternative embodiment, the S-shaped confinement ring 130 may be made in multiple pieces, as described with reference to FIG. 6B.

[0086] FIG. 2B illustrates an alternative embodiment of the plasma processing chamber 100′ in which the S-shaped confinement ring 130 is disposed. Various components common between the plasma processing chamber 100 of FIG. 2A and the plasma processing chamber 100′ of FIG. 2B are represented using the same reference numerals and perform similar functions. FIG. 2B illustrates an alternative structure of the outer electrode 102b′, in which the bottom surface of the outer electrode 102b′ includes a sloped profile. Although it is not necessary to redesign other hardware components in the plasma processing chamber 100 to accommodate the S-shaped confinement ring 130, in some embodiments, some of the hardware components may be redesigned, and such redesign may be performed to further reduce the volume in the plasma region 108 for receiving plasma. In the embodiment illustrated in FIG. 2B, the outer electrode 102b′ includes a top surface 103a and a bottom surface 103b′. The top surface 103a is flat and the bottom surface 103b' is defined by a slope in at least a portion of the bottom surface 103b', which may be the entirety of the bottom surface 103b' or less than the entirety of the bottom surface 103b'. In the embodiment shown in FIG. 2B, for example, the bottom surface 103b' is defined by a first flat lower section 103c1, a sloped lower section 103c2, and a second flat lower section 103c3. The first flat lower section 103c1 is defined on an inner side disposed adjacent to the upper electrode 102a and extends over a first length.

[0087] In one embodiment, the first flat lower section 103c1 may include an angled or rounded inner edge defined adjacent the top electrode 102a. The gradient lower section 103c2 is disposed adjacent the first flat lower section 103c1 and extends over the second length. The second flat lower section 103c3 is disposed adjacent the gradient lower section 103c2 such that the gradient lower section 103c2 is defined between the first flat lower section 103c1 and the second flat lower section 103c3. The second flat lower section 103c3 extends to the outer edge of the outer electrode 102b' and covers the third length. The gradient lower section 103c2 includes a slope extending downward from the first flat lower section 103c1 toward the second flat lower section 103c3. In one embodiment, the inclination angle of the gradient lower section 103c2 and the angle of the angled inner edge (if present) of the outer electrode 102b' may be defined to allow the plasma to flow freely within the plasma region 108. The angle of the gradient lower section 103c2 creates a height difference on the inside and outside of the outer electrode 102b', where the inner height of the outer electrode 102b' is smaller than the outer height of the outer electrode 102b'. As a result, the outside of the outer electrode 102b' adjacent to the inside of the upper vertical section 132 covers a portion of the upper vertical section 132 of the S-shaped confinement ring 130. The difference in height from the inside to the outside of the outer electrode 102b' depends on the inclination angle of the gradient lower section 103c2. In one embodiment, the length of each of the sections, i.e., the first flat lower section 103c1, the gradient lower section 103c2, and the second flat lower section 103c3, is equal. In an alternative embodiment, the length of each of the sections is different. For example, the lengths of the first and second flat lower sections 103c1, 103c3 may be equal, and the length of the gradient lower section 103c2 may be less than or greater than the length of the first and second flat lower sections 103c1, 103c3. The gradient lower section 103c2 further reduces the volume within the plasma region 108. As a result, less plasma is needed within the plasma region 108 to perform a fabrication operation.Even though the volume is reduced, plasma density is improved because more plasma is contained within the smaller internal volume of plasma region 108, and plasma uniformity and gas conductance are maintained at optimal levels in the plasma volume of plasma region 108.

[0088] FIG. 3A illustrates a perspective view of a top surface of an S-shaped confinement ring 130 used in the plasma processing chamber 100 in one embodiment, and FIG. 3B illustrates a perspective view of a bottom surface of the S-shaped confinement ring 130 in one embodiment. Referring initially to FIG. 3A, the S-shaped confinement ring 130 includes an upper horizontal section 131 having a plurality of holes 137 defined therein, each hole configured to receive a portion of a fastening mechanism, such as a cam key. The fastening mechanism is not limited to a cam lock structure, but may include other fastening mechanisms, such as a screw. In some embodiments, the holes 137 for receiving the plurality of cam keys are uniformly distributed on the top surface 131a, and the cam keys are used to couple the confinement ring 130 to the upper electrode structure 102 via corresponding cam locks defined in the bottom surface of the backing plate 105. The upper horizontal section 131 extends between a first outer radius and a top of an upper vertical section 132 defined at or proximate to an inner upper radius of the confinement ring 130. The upper vertical section 132 extends between the upper horizontal section 131 and the middle section 133. The middle section 133 extends between a bottom of the upper vertical section 132 and a top of a lower vertical section 134 defined at or proximate to a second outer radius. The lower horizontal section 135 extends between a bottom of the lower vertical section 134 and an inner lower radius. The lower horizontal section includes a plurality of conductance slots (or simply referred to hereinafter as "slots") 140. The slots 140 extend radially on a surface of the lower horizontal section 135 from an inner diameter to an outer diameter. The inner diameter of the slots 140 is larger than an inner ring diameter of the confinement ring 130, the inner ring diameter being defined by an inner lower radius. The outer diameter of the slots is larger than the inner ring diameter and the inner diameter but smaller than an outer ring diameter of the confinement ring 130, the outer ring diameter being defined by a second outer radius. In the embodiments shown in Figures 2A, 2B, 3A, and 3B, the first outer radius is less than the second outer radius. In alternative embodiments, the first outer radius may be greater than or equal to the second outer radius.In the embodiment shown in FIG. 3A, upper horizontal section 131, upper vertical section 132, middle section 133, lower vertical section 134, and lower horizontal section 135 of confinement ring 130 form a unitary structure (i.e., a single continuous unit) together.

[0089] FIG. 3B illustrates a number of slots 140 defined in the lower horizontal section 135. In the embodiment shown in FIG. 3B, the slots 140 are defined to include a parallel slot geometry. In an alternative embodiment, the slots 140 may be defined to include a tapered slot geometry, with the tapered slot defined by a wide side defined by an outer diameter of the confinement ring 130 and a narrow side defined by an inner diameter. The wide side of the slot is defined by an outer slot radius that is larger than the narrow side defined by an inner slot radius. The size of the inner and outer slot radii are defined to be the inverse of the wear rate at the corresponding inner and outer diameters of the slots 140. In one embodiment, one or more optical emission spectroscopy (OES) holes 138 are defined in the lower vertical section 134. The OES holes 138 are provided with probes that are used to monitor the plasma in the plasma region 108 and the effect of the plasma on the top surface of the substrate 110. Results from the probes located in the OES holes 138 are used for endpoint detection.

[0090] FIG. 4 illustrates an overhead view of the top surface of an S-shaped confinement ring 130 used in a plasma processing chamber in one embodiment. FIG. 4 identifies several features of the confinement ring 130. For example, as shown, the upper horizontal section 131 extends from a first outer radius 150 to an inner upper radius 152. The lower horizontal section 135 extends from a second outer radius 151 to an inner lower radius 153. The second outer radius 151 is larger than the first outer radius 150, and the inner lower radius 153 is smaller than the inner upper radius 152 (i.e., the inner lower radius 153<the inner upper radius 152<the first outer radius 150<the second outer radius 151). The inner lower radius 153 defines an inner ring diameter of the confinement ring 130, and the second outer radius 151 defines an outer ring diameter of the confinement ring 130. Figure 4 shows a number of holes 137 for receiving a cam key (i.e., part of the locking mechanism) distributed on a top surface of the upper horizontal section 131. In some embodiments, the upper horizontal section 131 overhangs a portion of the middle section 133, which in turn overhangs a portion of the lower horizontal section 135 that includes the slot 140. Figure 4 illustrates the relative overhangs of the upper horizontal section 131 and the middle section 133. A cross-sectional view of section AA of Figure 4 is shown and described in detail with reference to Figure 5, and a cross-sectional view of section CC of Figure 4 is shown and described in detail with reference to Figures 6A-6D.

[0091] FIG. 5 illustrates a cross-sectional view of section AA identified in FIG. 4 in one embodiment. The cross-sectional view identifies various features of the S-shaped containment ring 130. In some embodiments, an upper inner diameter (IUD1) defined by an inner upper radius of the upper horizontal section 131 is defined to be about 420 mm (about 16.54 inches) to about 432 mm (about 17.01 inches). In some embodiments, a first outer diameter (OD1) defined by a first outer radius about which the upper horizontal section 131 extends is defined to be about 500 mm (about 19.7 inches) to about 516 mm (about 20.3 inches). In some embodiments, a second outer diameter (OD2) about which the middle section 133 extends is defined to be about 510 mm (about 20.08 inches) to about 530 mm (about 20.87 inches). In some embodiments, the outer diameter (ODs1) of the step 148 defined in the upper horizontal section 131 of the containment ring 130 is defined to be between about 426 mm (about 16.77 inches) and about 438 mm (about 17.24 inches). In some embodiments, the inner diameter of the inside of the upper vertical section 132 is defined to be the same as the upper inner diameter of the upper horizontal section 131. In some embodiments, the outer diameter (ODvs1) of the upper vertical section 132 is defined to be between about 430 mm (about 16.93 inches) and about 448 mm (about 17.64 inches). In some embodiments, the thickness of the upper vertical section 132 is defined to be between about 10 mm (about 0.39 inches) and about 16 mm (about 0.63 inches). In some embodiments, the inner diameter (IDvs2) of the lower vertical section 134 is defined to be between about 500 mm (about 19.69 inches) and about 516 mm (about 20.32 inches), and the outer diameter of the lower vertical section 134 is defined by a second outer diameter (OD2). In some embodiments, the thickness of the lower vertical section 134 is defined to be between about 10 mm (about 0.39 inches) and about 14 mm (about 0.55 inches). In some embodiments, the inner lower diameter (ILD1) about which the lower horizontal section 135 extends (i.e., equal to the inner lower radius x 2) is defined to be between about 370 mm (about 14.57 inches) and about 385 mm (about 15.16 inches).The aforementioned ranges for the various features of the S-shaped confinement ring 130 are provided by way of example only and should not be considered limiting. Other ranges for the various features or adjustments to the aforementioned ranges may be envisioned, and such ranges or adjustments may be based on the inner dimensions of the plasma processing chamber 100, the type of process being performed, the type of process gas used to generate the plasma, the amount of area desired within the interior volume of the plasma region for the plasma, the types of by-product and neutral gas species to be generated and removed, the access openings of the plasma processing chamber, the geometry of the hardware components of the plasma processing chamber, etc. In the diagram of FIG. 5, the S-shaped confinement ring 130 is shown as having a middle section and a lower horizontal section with a flat profile.

[0092] FIG. 6A illustrates an enlarged cross-sectional view of an S-shaped containment ring 130 in one embodiment. In the cross-sectional view shown, the slot 140 is located in the lower horizontal section 135. The cross-sectional view identifies the heights of different components of the containment ring 130. For example, a height h1 is defined between a top surface 135a of the lower horizontal section 135 and a bottom surface 133b of the middle section 133 proximate the second outer radius of the containment ring 130. In one embodiment, the height h1 is defined to be between about 10 mm (about 0.39 inches) and about 40 mm (about 1.57 inches). A height h2 is defined between a top surface 133a of the middle section 133 and a bottom surface 131b of the upper horizontal section 131. In one embodiment, the height h2 is defined to be between about 10 mm (about 0.39 inches) and about 40 mm (about 1.57 inches). A height h3 is defined between a top surface 135a of the lower horizontal section 135 and a bottom surface 133b of the middle section 133 proximate the inner top radius of the containment ring 130. In one embodiment where the lower horizontal section 135 is flat, the height h3 is defined to be equal to the height h1. In an alternative embodiment where the lower horizontal section 135 has a sloped top surface 135a, the height h3 may be greater than the height h1. The step 148 defined in the top surface of the upper horizontal section at the inner top radius has a height h4. In one embodiment, the height h4 is defined to be about 0.15 inches to about 0.18 inches. The upper vertical section 132 of the S-shaped containment ring 130 is defined to extend over a height h5. In one embodiment, height h5 is defined to be between about 28 mm (about 1.10 inches) and about 34 mm (about 1.34 inches). Height h6 is defined between top surface 131a of upper horizontal section 131 and top surface 135a of lower horizontal section 135. In one embodiment, height h6 is defined to be between about 45 mm (about 1.77 inches) and about 53 mm (about 2.09 inches). Height h7 is defined between top surface 131a of upper horizontal section 131 and a bottom surface of vertical extension 136. In one embodiment, height h7 is defined to be between about 56 mm (about 2.20 inches) and about 65 mm (about 2.56 inches).A height h8 is defined relative to a hole 137 defined in the top surface 131a of the upper horizontal section 131 in which a portion of a locking mechanism, such as a cam key, may be placed. In one embodiment, the height h8 is defined to be between about 0.18 inches and about 0.21 inches. The thickness of the upper horizontal section 131 is defined by a height h9. In one embodiment, the height h9 is defined to be between about 0.29 inches and about 0.32 inches. A height h10 is defined between the top surface 131a of the upper horizontal section 131 and the top surface 133a of the middle section. In one embodiment, the height h10 is defined to be between about 0.83 inches and about 1.14 inches. A height h11 is defined between the top surface 131a of the upper horizontal section 131 and the bottom surface 135b of the lower horizontal section 135. In one embodiment, the height h11 is defined to be about 50 mm (about 1.97 inches) to about 60 mm (about 2.36 inches). In the embodiment shown in FIG. 6A, the top surface 133a and the bottom surface 133b of the middle section 133 are defined to be flat. As a result, the thickness t1 of the middle section 133 proximate the inner upper radius is equal to the thickness t2 of the middle section 133 proximate the second outer radius (i.e., the middle section has a uniform thickness along its length). In this case, the thicknesses t1 and t2 are defined to be about 12 mm (about 0.47 inches) to about 20 mm (about 0.79 inches), according to some embodiments. The upper horizontal section 131 extends from the outer side of the upper vertical section 132 over a length l1. In one embodiment, length 11 is defined to be between about 29 mm (about 1.14 inches) and about 38 mm (about 1.50 inches). In one embodiment, vertical extension 136 extends downwardly from bottom surface 135b of lower horizontal section 135 by about 3 mm (about 0.12 inches) to about 7 mm (about 0.28 inches). The S-shaped containment ring 130 shown in FIG. 6A is a unitary piece, with upper horizontal section 131, upper vertical section 132, middle section 133, lower vertical section 134, and lower horizontal section 135 forming a single continuous piece together.A vertical extension 136 extends downwardly from the lower horizontal section 135 proximate the inner lower radius. The aforementioned ranges for the various components of the S-shaped confinement ring 130 are provided by way of example only and should not be considered limiting. Other ranges for the various components or adjustments to the aforementioned ranges may also be envisioned.

[0093] FIG. 6B shows an alternative embodiment of the S-shaped confinement ring 130 of FIG. 6A. In the embodiment shown in FIG. 6B, the S-shaped confinement ring 130' is made of two pieces. The lower horizontal section 135 of the S-shaped confinement ring 130, including the slots 140, is the part that is highly susceptible to wear (i.e., has a short service life) due to exposure to plasma and by-products, while the remaining sections of the S-shaped confinement ring 130 can last longer (i.e., has a longer service life) than the lower horizontal section 135. Thus, to maximize the service life of the confinement ring, the confinement ring 130' can be designed to be made of two pieces. For example, the upper horizontal section 131, the upper vertical section 132, the middle section 133, and the lower vertical section 134 together define a single, integral first piece (i.e., piece 1), and the lower horizontal section 135 and the vertical extension 136 define a second piece (i.e., piece 2). The first piece may be received on an RF gasket 139 disposed on a top surface 135a of the lower horizontal section 135 of the second piece proximate the second outer radius. The RF gasket 139 provides a tight bond between the two pieces when they are assembled together in the plasma processing chamber 100 and provides a path for RF current to ground (similar to the RF gasket 116 defined on the top surface of the floating element 124b of the grounded bucket 124 disposed on the lower electrode 104). In the embodiment shown in FIG. 6B, the height h1 between the bottom surface 133b of the middle section 133 and the top surface 135a of the lower horizontal section 135 proximate the second outer radius may be varied by including a slope in the bottom portion 133a of the middle section 133. In other alternative embodiments, the S-shaped confinement ring 130 may be composed of three or more pieces, with each piece connected to the next piece, for example, via an RF gasket disposed on the next piece.

[0094] FIG. 6C illustrates another alternative embodiment of an S-shaped confinement ring 130″ disposed in the plasma processing chamber 100. FIG. 6C illustrates an enlarged view of section CC of the S-shaped confinement ring 130 identified in FIG. 4. In this embodiment, the S-shaped confinement ring 130″ includes a middle section 133′ having a different geometric profile than the middle section 133 shown in FIGS. 6A and 6B. The middle section 133′ is defined by a top surface 133a and a bottom surface 133b′. In the embodiment of FIG. 6C, the top surface 133a is defined as a flat surface, while the bottom surface 133b′ has a slope extending downward from the upper vertical section 132 (i.e., from the inner upper radius) to the lower vertical section 134 (i.e., to the second outer radius). The slope angle can be defined based on the amount of interior volume 108b desired within the plasma region 108. In some implementations, the amount of interior volume 108b that is reduced can depend, for example, on the type of gas in the plasma region 108. In this implementation, the top and bottom surfaces (131a, 131b, 135a, 135b) of both the upper horizontal section 131 and the lower horizontal section 135 are flat, except for an inner edge of the top surface of the upper horizontal section 131 that includes a step 148 configured to support a lip extension of the outer electrode 102b. The slope defined in the middle section 133' creates a difference in height adjacent the inner top radius and the second outer radius, as well as a difference in thickness along the length of the middle section 133'. For example, the height h1' defined between the top surface 135a of the lower horizontal section 135 and the sloped bottom surface 133b' of the middle section 133' adjacent the second outer radius is smaller than the height h3 defined between the top surface 135a of the lower horizontal section 135 and the sloped bottom surface 133b' of the middle section 133' adjacent the inner upper radius, while in the embodiment shown in Figures 6A and 6B, the heights h1 and h3 are shown to be equal. The height h2 between the bottom surface 131b of the upper horizontal section 131 and the top surface 133a of the middle section 133' adjacent the inner upper radius remains the same as in the embodiment shown in Figures 6A and 6B.Similarly, thickness t1 of middle section 133' proximate the inner top radius is less than thickness t2' of middle section 133' proximate the second outer radius. The difference in thickness is due to tilting. The amount of difference depends on the tilt angle defined in bottom surface 133b' of middle section 133'. In one embodiment, thickness t2 is defined to be about 10% to about 40% greater than thickness t1. The tilting in middle section 133' provides a way to reduce the volume in plasma region 108 for receiving plasma without requiring redesign of other hardware components of plasma processing chamber 100 and without compromising the mechanical strength or service life of confinement ring 130''.

[0095] FIG. 6D illustrates an enlarged cross-sectional view of an S-shaped confinement ring 130''' used in the plasma processing chamber 100 in one embodiment. In this embodiment, the S-shaped confinement ring 130''' includes different geometric profiles for the middle section and the lower horizontal section. For example, the S-shaped confinement ring 130''' includes a middle section 133' having a slope defined at a bottom surface 133b' that extends downwardly from the inner upper radius to the second outer radius (similar to the geometric profile of the middle section 133' shown in FIG. 6C) and a lower horizontal section 135' that includes a slope at a top surface 135a' that extends downwardly from the second outer radius to the inner lower radius of the confinement ring 130'''. In addition to the slope at the top surface 135a', a second slope is defined at a bottom surface 135b' of the lower horizontal section 135' that extends downwardly from the second outer radius to the inner lower radius. In one embodiment, the inclination angle of the top surface 135a' of the lower horizontal section 135' may be equal to the second inclination angle defined on the bottom surface 135b' of the lower horizontal section. In an alternative embodiment, the inclination angle of the top surface 135a' of the lower horizontal section 135' may be less than or greater than the second inclination angle defined on the bottom surface 135b' of the lower horizontal section 135'. Further, in one embodiment, the inclination angle of the bottom surface 133b' of the middle section 133' may be equal to the inclination angle of the top surface 135a' of the lower horizontal section 135'. In an alternative embodiment, the inclination angle of the bottom surface 133b' of the middle section 133' may be greater than or less than the inclination angle of the top surface 135a' of the lower horizontal section 135'. In another embodiment, the top surface 135a' of the lower horizontal section 135 is defined to include a slope extending downwardly from the second outer radius to the inner lower radius, and the bottom surface 135b of the lower horizontal section 135 is defined to be flat. In this embodiment, the thickness of the lower horizontal section 135 varies along the length of the lower horizontal section 135, with the thickness proximate the second outer radius being greater than the thickness proximate the inner lower radius of the lower horizontal section 135. The amount of slope in the lower horizontal section 135 may be defined to ensure that the mechanical strength of the S-shaped confinement ring 130 is not compromised.

[0096] Due to the slopes defined in both the middle section 133' and the lower horizontal section 135', the heights h1 and h3 may vary. As a result, in the embodiment shown in FIG. 6D, the height h1'' defined between the top surface 135a' of the lower horizontal section 135' and the bottom surface 133b' of the middle section 133' at the second outer radius is less than the height h3 defined between the top surface 135a' of the lower horizontal section 135' and the bottom surface 133b' of the middle section 133' at the inner upper radius. The height h3 may be equal to, greater than, or less than the height h2 defined between the top surface 133a of the middle section 133 and the bottom surface 131b of the upper horizontal section 131. In the cross-sectional view of FIG. 6D shown, a slot 140 is defined in the lower horizontal section 135'. It should be noted that in the embodiment shown in Figures 6C and 6D, the slope along the bottom surface of middle section 133' and the top and bottom surfaces of lower horizontal section 135' may be exaggerated to show the presence of throw, and the actual angle of each slope may be less than that shown.

[0097] In one embodiment, the tilt angle defined at the bottom surface of the middle section 133 with respect to the horizontal x-axis may be defined to be equal to the tilt angle defined at the top surface of the lower horizontal section 135. In an alternative embodiment, the tilt angle at the bottom surface of the middle section 133 with respect to the horizontal x-axis may be defined to be greater than the tilt angle defined at the top surface of the lower horizontal section 135. The aforementioned ranges for the tilt angles at the middle section 133 and the lower horizontal section 135 are provided by way of example only and should not be considered limiting. As a result, in some embodiments, the tilt angles at the middle section 133 and / or the lower horizontal section 135 may be envisioned to be greater or less than the aforementioned ranges, and such increases or decreases in angles may be based on the inner dimensions of the plasma processing chamber 100, the type of process being performed, the amount of interior volume 108a desired within the plasma region 108, the type of process gas used to generate the plasma, the type of by-product and neutral gas species that are generated and need to be removed, the access openings of the plasma processing chamber, etc. In one embodiment, the confinement rings 130 are made of silicon. In other embodiments, the confinement rings may be made of polysilicon, or silicon carbide, or boron carbide, or ceramic, or aluminum, or any other material that can withstand the processing conditions of the plasma region 108.

[0098] The lower horizontal section 135 includes a vertical extension 136 defined proximate the inner lower radius. In one embodiment shown in FIGS. 6A-6D, the inner edge of the vertical extension 136 is defined by a right angle. In an alternative embodiment, the inner edge of the vertical extension 136 can include an angled top section (angled on the inside defined by the inner lower radius) and a vertical bottom section. The angled top section includes a slope on the inner edge defined by the inner lower radius. The vertical bottom section is disposed below the angled top section and extends vertically downward for a height above the bottom surface 135b of the lower horizontal section 135. The vertical extension 136 provides continuity to the lower horizontal section 135. The bottom surface of the vertical bottom section is configured to rest on the RF gasket 116 disposed on the top surface of the ground bucket 124 defined in the lower electrode 104 in this embodiment.

[0099] FIG. 7 shows an overhead view of the bottom surface of the lower horizontal section 135 of the S-shaped confinement ring 130 used in the plasma processing chamber 100. The overhead view shows slots 140 extending radially between the inner and outer diameters. The slots 140 effectively confine the plasma in the plasma region 108 while directing by-products out of the plasma region 108. The slots 140 extend from the top surface 135a to the bottom surface 135b of the lower horizontal section 135. The slots 140 may have a parallel slot profile, or a tapered slot profile, or a curved slot profile. Details of the parallel slot profile, the tapered slot profile, and the curved slot profile are described with reference to FIGS. 8A-8D.

[0100] FIG. 8A shows an expanded view of Detail H identified in FIG. 7. Detail H shows an expanded view of the slot 140 defined along the lower horizontal section 135 of the S-shaped containment ring 130. As discussed with reference to FIGS. 2-6D, the lower horizontal section 135 extends from a second outer radius to an inner lower radius. The slot 140 extends radially over a slot length "ls1" between an inner diameter (ID1) and an outer diameter (OD1) defined on the lower horizontal section 135. In one embodiment, the slot length ls1 is defined to be between about 40 mm (about 1.58 inches) and about 75 mm (about 2.95 inches). In some embodiments, the inner diameter (ID1) of the slot 140 is greater than an inner ring diameter (IRD) defined by the inner lower radius of the lower horizontal section 135. In some embodiments, the outer diameter (OD1) of the slot 140 is greater than the ID1 and the IRD, but less than an outer ring diameter (ORD) defined by the second outer radius of the lower horizontal section 135.

[0101] FIG. 8B shows an expanded view of one of the slots 140 defined in the lower horizontal section 135 of the S-shaped confinement ring 130 in one embodiment. The slots 140 are used to direct by-products out of the plasma region 108 while effectively confining the plasma within the plasma region 108, and are therefore also referred to as conductance slots. Each slot 140 is defined in this embodiment to have a parallel slot profile. Thus, the inner slot radius (ISR) 140c at the inner diameter (ID1) 140a is equal to the outer slot radius (OSR) 140d at the outer diameter (OD1) 140b, and the width of the slot 140 defined by the ISR and OSR is uniform along the length ls1 of the slot 140. When wear at ID1 140a or OD1 140b reaches a critical dimension, the confinement ring 130 may have to be replaced to avoid the occurrence of a plasma deconfinement event.

[0102] FIG. 8C illustrates an expanded view of a slot 140′ defined in the lower horizontal section 135 of the S-shaped confinement ring 130, in one embodiment, where the slot 140′ is defined to have a tapered slot profile. The tapered slot profile includes a taper that tapers downward from the outer diameter (OD1) 140b to the inner diameter (ID1) 140a such that the slot 140′ is wider at OD1 140b and narrower at ID1 140a. In this embodiment, an inner slot radius (ISR) 140c′ at the inner diameter (ID1) 140a is defined to be smaller than an outer slot radius (OSR) 140d′ at the outer diameter (OD1) 140b. In one embodiment, the ratio of the ISR 140c′ to the OSR 140d′ may be defined to be about 1:1.1 to about 1:1.5. This ratio is provided by way of example only, and other ratios may be envisioned. To compensate for the narrow ISR 140c', in one embodiment, the length ls1 of the slots 140' can be increased to provide additional slot area for by-products and neutral gas species to escape from the plasma region 108. In an alternative embodiment, in addition to or instead of increasing the length ls1, the number of slots 140' may be increased to compensate for the narrow ISR 140c'.

[0103] The amount of taper defined by ISR 140c' and OSR 140d' is defined to be the inverse of the corresponding wear rate at ID1 140a and OD1 140b. Wear along the length of slot 140' is non-uniform due to the amount different portions along the length of slot 140' are exposed to plasma in plasma region 108, and the area of ​​slot 140' at ID1 140a wears more than the area of ​​slot 140' at OD1 140b. Because slot wear varies along the slot length, sizing the slot taper as a function of wear rate ensures that a high wear rate at ID1 140a is compensated for by a low wear rate at OD1 140b, resulting in a nearly straight slot profile at the end of the confinement ring's life. The tapered profile of the slots 140' provides more area at ID1 140a than OD1 140b for slot wear, so that the tapered slots 140' as a whole may reach a critical dimension at about the same time that the confinement ring 130' requires replacement. Additional slots may be defined to compensate for the open area in the lower horizontal section due to the reduction in the slot dimensions at the inner diameter. The number of additional slots may be defined by considering the amount of wear space required at the narrow and wide ends for each slot 140' to reach a critical dimension. The tapered slot geometry extends the amount of wear the slots can tolerate before reaching the limit of uncontainment, resulting in longer service life and improved consumable costs. Even though the slots 140' have a tapered slot profile, the size of the ISRs 140c' and OSRs 140d' are defined to allow for removal of by-products and neutral gas species from the plasma region 108. Slot 140 in FIG. 8B and slot 140' in FIG. 8C are not drawn to scale and are exaggerated to show the different dimensions.

[0104] For further information regarding the use of tapered slot profiles to define the slots 140' along the lower horizontal section 135 of the confinement ring, reference may be made to commonly owned and co-pending International Patent Application No. PCT / US20 / 053894, filed October 30, 2020, entitled "Wear Compensating Confinement Ring," which is incorporated herein by reference in its entirety. Variations in the design of the confinement ring 130, such as defining a slope along the top surface 135a of the lower horizontal section 135 and the slots 140 having a parallel slot profile, or defining a slope along the top surface 135a of the lower horizontal section 135 and the slots 140' having a tapered slot profile, may also be envisioned to improve plasma density over the length of the substrate surface.

[0105] FIG. 8D illustrates an expanded view of a slot 140″ defined in the lower horizontal section 135 of the S-shaped confinement ring 130 in yet another embodiment, where the slot 140″ is defined to include a curved slot profile. Although not shown in FIG. 8A, the curved slot profile can also be used to increase the length ls1 of the slot 140″ for escaping by-products. The angle of curvature of the curved slot 140″ can be based on the amount of length the slot 140″ needs to be increased to efficiently direct the by-products out of the plasma region 108. The curved slot 140″ can include, in one embodiment (not shown), a parallel slot profile with an inner slot radius 140c at ID1 140a equal to an outer slot radius 140d at OD1 140b as described with reference to FIG. 8B, but the slot profile is curved along the length of the slot 140″. In an alternative embodiment shown in FIG. 8D, the curved slot 140″ may include a tapered slot profile in which the ISR 140c′ at ID1 140a is smaller than the OSR 140d′ at OD1 140b as described with reference to FIG. 8C, but the slot profile is curved along the length of the slot 140″. As can be seen, there may be variations in the shape of the slot defined in the lower horizontal section 135. The variations in shape may be based on the type of gas used to generate the plasma, the type of by-products being removed, the amount of area needed to remove the by-products from the plasma region, optimal plasma confinement within the plasma region, etc. The slot shapes and different sizes shown in FIGS. 8B-8D are some examples and other shapes and sizes for the slot may be envisioned.

[0106] Advantages of the S-shaped confinement ring described in various embodiments include improved plasma density uniformity without adversely affecting other hardware components (e.g., chamber spacer plates, mating hardware, etc.) or the mechanical strength or service life of the confinement ring. Additionally, the S-shape helps reduce the volume in the plasma region, which results in less gas being required to generate the plasma to fill the reduced volume of the plasma region, thereby conserving process gases used. Modifications to the shape of different surfaces of the confinement ring (i.e., sloping the bottom surface of the middle section and / or the top surface of the lower horizontal section) can be made to further tailor the volume and plasma density uniformity without affecting the strength or inherent service life of the confinement ring. This allows the confinement ring to withstand more process operations along the lower horizontal section and along the length of the slot before reaching a critical dimension limit, improving substrate etching uniformity and improving the cost of the consumable confinement ring. Other advantages will be envisioned by those skilled in the art upon consideration of the various embodiments described herein.

Claims

1. 1. A confinement ring for use in a plasma processing chamber, comprising: an upper horizontal section extending between an inner upper radius and a first outer radius; a middle section extending between the inner upper radius and a second outer radius; a lower horizontal section extending between an inner lower radius and the second outer radius; an upper vertical section extending between the upper horizontal section and the intermediate section proximate the inner upper radius; a lower vertical section extending between the intermediate section and the lower horizontal section proximate the second outer radius; a vertical extension extending downwardly from the lower horizontal section adjacent the inner lower radius; and A containment ring comprising:

2. 10. The confinement ring of claim 1, A plasma volume is disposed between an upper electrode structure, a lower electrode, and the confinement ring of the plasma processing chamber.

3. 3. The confinement ring of claim 2, A confinement ring, wherein an outer volume is defined between the upper horizontal section, the upper vertical section, and the middle section, the outer volume being outside the plasma volume.

4. 3. The confinement ring of claim 2, A confinement ring, wherein an interior volume is defined between the middle section, the lower vertical section, and the lower horizontal section, the interior volume being inside the plasma volume.

5. 10. The confinement ring of claim 1, an exterior volume is defined between the upper horizontal section, the upper vertical section, and the middle section; an interior volume is defined between the middle section, the lower vertical section, and the lower horizontal section, the interior volume being inside a plasma volume of the plasma processing chamber, the exterior volume being outside the plasma volume, and the exterior volume reducing the plasma volume; Confinement ring.

6. 10. The confinement ring of claim 1, The upper horizontal section, the upper vertical section, the middle section, the lower vertical section, and the lower horizontal section together define an S-shaped structure.

7. 10. The confinement ring of claim 1, A confinement ring, wherein the length of the middle section and the length of the lower horizontal section are of uniform thickness.

8. 10. The confinement ring of claim 1, a top surface of the intermediate section includes a flat profile and a bottom surface of the intermediate section is angled downwardly from the inner upper radius toward the second outer radius, and a first thickness of the intermediate section proximate the inner upper radius is less than a second thickness of the intermediate section proximate the second outer radius.

9. 10. The confinement ring of claim 1, a first height defined between a top surface of the lower horizontal section and a bottom surface of the middle section proximate the second outer radius is less than a second height defined between a top surface of the middle section and a bottom surface of the upper horizontal section proximate the inner upper radius.

10. 10. The confinement ring of claim 1, a first height defined between a top surface of the lower horizontal section and a bottom surface of the middle section proximate the second outer radius, the first height being equal to a second height defined between a top surface of the middle section and a bottom surface of the upper horizontal section proximate the inner upper radius, and a third height defined between the top surface of the lower horizontal section and the bottom surface of the middle section proximate the inner upper radius.

11. 10. The confinement ring of claim 1, the second outer radius extends beyond the first outer radius, the second outer radius defining an outer radius of the confinement ring; the inner upper radius is greater than the inner lower radius; Confinement ring.

12. 10. The confinement ring of claim 1, the lower horizontal section includes a plurality of slots, each slot of the plurality of slots extending radially along the lower horizontal section from an inner diameter to an outer diameter, the inner diameter of each slot being greater than an inner ring diameter of the confinement ring defined by the inner lower radius and the outer diameter of the slot being less than an outer ring diameter of the confinement ring defined by the second outer radius, and each slot extending from a top surface to a bottom surface of the lower horizontal section.

13. 13. The confinement ring of claim 12, an inner slot radius of each slot at the inner diameter is less than an outer slot radius of each slot at the outer diameter; a difference between the inner and outer slot radii of each slot defines a slot taper, each slot tapering downward from the outer diameter to the inner diameter, the inner and outer slot radii affecting the slot taper being defined to be the inverse of the wear rates at the corresponding inner and outer diameters of the slot. Confinement ring.

14. 13. The confinement ring of claim 12, A ratio of the inner slot radius to the outer slot radius is from about 1:1.1 to about 1:1.

5.

15. 13. The confinement ring of claim 12, a containment ring wherein an inner slot radius of each slot at said inner diameter is equal to an outer slot radius of each slot at said outer diameter.

16. 10. The confinement ring of claim 1, A confinement ring, wherein a first height of the upper vertical section is equal to a second height of the lower vertical section.

17. 10. The confinement ring of claim 1, A confinement ring, wherein a first height of the upper vertical section is different from a second height of the lower vertical section.

18. 10. The confinement ring of claim 1, a confinement ring, the upper horizontal section, the upper vertical section, the middle section, the lower vertical section, and the lower horizontal section forming an integral S-shaped structure, the vertical extension defined proximate the inner lower radius integrally continuing downwardly with the S-shaped structure, the integral S-shaped structure configured to confine a plasma within a plasma region defined in the plasma processing chamber.

19. 10. The confinement ring of claim 1, the upper horizontal section, the upper vertical section, the middle section, and the lower vertical section define a first unitary piece, and the lower horizontal section defines a second piece; the first unitary piece is configured to be received over a radio frequency gasket defined on a top surface disposed proximate the second outer radius of the second piece. Confinement ring.

20. 10. The confinement ring of claim 1, A confinement ring, wherein the lower horizontal section includes a slope extending downwardly from the lower vertical section toward the inner lower radius, and a thickness along the length of the lower horizontal section is uniform.

21. 10. The confinement ring of claim 1, the vertical extension is defined by an angled top section and a vertical bottom section, the angled top section being defined at a top surface of the lower horizontal section proximate the inner lower radius and the vertical bottom section being defined extending downwardly from a bottom portion of the angled top section proximate the inner lower radius.

22. 10. The confinement ring of claim 1, The lower vertical section of the confinement ring includes one or more optical emission spectroscopy (OES) holes in which probes are positioned to monitor plasma in the plasma processing chamber for endpoint detection.

23. 10. The confinement ring of claim 1, A confinement ring, wherein a top surface of the upper horizontal section includes a plurality of holes that receive cam keys for coupling the confinement ring to corresponding cam locks disposed on a bottom surface of a backing plate disposed in the plasma processing chamber, each cam key being positioned to align with a corresponding cam lock.

24. 1. A confinement ring for use in a plasma processing chamber, comprising: an upper horizontal section extending between an inner upper radius and a first outer radius; an intermediate section extending between the inner upper radius and a second outer radius, a top surface of the intermediate section having a flat profile and a bottom surface of the intermediate section including a slope extending downwardly from the inner upper radius toward the second outer radius; a lower horizontal section extending between an inner lower radius and the second outer radius; an upper vertical section extending between the upper horizontal section and the intermediate section proximate the inner upper radius; a lower vertical section extending between the intermediate section and the lower horizontal section proximate the second outer radius; a vertical extension extending downwardly from the lower horizontal section adjacent the inner lower radius; and a confinement ring.

25. 25. The confinement ring of claim 24, a top surface of the lower horizontal section defined by a first slope extending downwardly from the lower vertical section toward the inner lower radius;

26. 26. The confinement ring of claim 25, a first height defined between the bottom surface of the middle section and the top surface of the lower horizontal section proximate the second outer radius is less than a second height defined between the bottom surface of the middle section and the top surface of the lower horizontal section proximate the inner lower radius.

27. 26. The confinement ring of claim 25, a bottom surface of the lower horizontal section defined to include a flat profile, the first slope of the lower horizontal section defining a variable thickness along a length of the lower horizontal section, the first thickness proximate the second outer radius being greater than a second thickness proximate the inner lower radius.

28. 26. The confinement ring of claim 25, a bottom surface of the lower horizontal section defined by a second slope extending downwardly from the lower vertical section toward the inner lower radius, a first slope angle of the first slope being equal to a second slope angle of the second slope, whereby a thickness along the length of the lower horizontal section is uniform.

29. 25. The confinement ring of claim 24, the upper horizontal section, the upper vertical section, the middle section, the lower vertical section, and the lower horizontal section together form an integral S-shaped structure, the vertical extension continuing downwardly with the S-shaped structure proximate the inner lower radius.

30. 25. The confinement ring of claim 24, the upper horizontal section, the upper vertical section, the middle section, and the lower vertical section define a first unitary piece, and the lower horizontal section defines a second piece; the first unitary piece is configured to be received over a radio frequency gasket defined on a top surface disposed proximate the second outer radius of the second piece. Confinement ring.

31. 25. The confinement ring of claim 24, the lower horizontal section includes a plurality of slots, each slot of the plurality of slots extending radially along the lower horizontal section from an inner diameter to an outer diameter, the inner diameter of the slot being greater than an inner ring diameter of the confinement ring defined by the inner lower radius and the outer diameter of the slot being less than an outer ring diameter of the confinement ring defined by the second outer radius, and each slot extending from a top surface to a bottom surface of the lower horizontal section.

32. 1. A plasma processing chamber for containing a plasma, comprising: a lower electrode disposed in a lower portion of the plasma processing chamber, the lower electrode including a support surface for supporting a substrate; an upper electrode structure disposed in an upper portion of the plasma processing chamber and facing opposite the lower electrode; a confinement ring coupled to a portion of the upper electrode structure and disposed between the upper electrode structure and the lower electrode, the confinement ring comprising: an upper horizontal section extending between an inner upper radius and a first outer radius; an intermediate section extending between the inner upper radius and a second outer radius; a lower horizontal section extending between an inner lower radius and the second outer radius; an upper vertical section extending between the upper horizontal section and the intermediate section adjacent the inner upper radius; a lower vertical section extending between the intermediate section and the lower horizontal section proximate the second outer radius; and a vertical extension extending downwardly from said lower horizontal section adjacent said inner lower radius; a confinement ring including 1. A plasma processing chamber comprising:

33. 33. The plasma processing chamber of claim 32, further comprising: A plasma processing chamber, wherein a plasma volume is disposed between the upper electrode structure, the lower electrode, and the confinement rings.

34. 31. The plasma processing chamber of claim 30, further comprising: The upper electrode structure includes: an upper electrode disposed at the center of the upper electrode structure; an outer electrode disposed adjacent to the upper electrode; a backing plate disposed to surround the outer electrode, the backing plate including an outer portion disposed adjacent the outer electrode such that the outer electrode is disposed between the upper electrode and the outer portion of the backing plate, and an inner portion disposed over a portion of the outer electrode, a bottom surface of the outer portion of the backing plate including a plurality of cam locks that align with corresponding ones of a plurality of cam keys disposed on a top surface of the upper horizontal section, the plurality of cam keys and the plurality of cam locks being a backing plate used to couple the outer electrode to the confinement ring; 1. A plasma processing chamber comprising:

35. 35. The plasma processing chamber of claim 34, further comprising: the plurality of cam keys are coupled to a controller configured to generate a first signal that actuates the plurality of cam keys to engage and lock the plurality of cam locks during coupling of the containment ring to the backing plate and a second signal that actuates the plurality of cam keys to allow unlocking of the plurality of cam locks during decoupling of the containment ring from the backing plate; the plurality of cam locks and the plurality of cam keys are part of an electronic cam lock mechanism configured to be controlled by signals from the controller. Plasma processing chamber.

36. 32. The plasma processing chamber of claim 31 , further comprising: A plasma processing chamber, wherein the backing plate and the upper electrode of the upper electrode structure are electrically grounded, and the lower electrode is coupled to a radio frequency (RF) generator through a corresponding matching network, the RF generator supplying RF power to the lower electrode to generate a plasma in the plasma processing chamber.

37. 32. The plasma processing chamber of claim 31 , further comprising: The upper horizontal section, the upper vertical section, the middle section, the lower vertical section, and the lower horizontal section together define an integral S-shaped structure.

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