C-shroud modification for plasma uniformity without affecting mechanical strength or lifetime

Abstract

SOLUTION: A confinement ring for use in a plasma processing chamber includes an upper horizontal portion, a vertical portion, and a lower horizontal portion, in which the upper horizontal portion extends between an upper inner radius and an outer radius of the confinement ring, the lower horizontal portion extends between a lower inner radius and an outer radius of the confinement ring and includes an extension portion extending to the lower inner radius, an upper surface of the lower horizontal portion provides an angle that descends toward the lower inner radius, the vertical portion is disposed between the outer radius and the inner radius of the confinement ring, and the vertical portion connects the upper horizontal portion to the lower horizontal portion of the confinement ring.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In semiconductor processing, substrates undergo various operations to form features that define integrated circuits. For example, for deposition operations, the substrate is received in a processing chamber, a specific type of reactive gas is supplied to the chamber depending on the type of feature to be formed, and radio frequency power is applied to generate a plasma. The substrate is received on a substrate support defined by a lower electrode, such as an electrostatic chuck. An upper electrode, such as a showerhead, is used to provide the specific type of reactive gas to the processing 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 on the substrate surface to form the fine features. The reactive gas generates by-products, such as particulates and gases, which must be rapidly removed from the plasma chamber to maintain the integrity of the fine features formed on the substrate surface.

[0003] To confine the generated plasma within the processing region, a set of confinement rings is defined to surround the processing region. Furthermore, to improve yield and ensure that the majority of the plasma is above the substrate accepted for processing, the confinement rings surrounding the plasma region may be configured to expand the processing region to cover not only the area above the substrate when the substrate is accepted for processing, but also the area above the edge ring and an outer confinement ring disposed adjacent to the edge ring. The set of confinement rings not only function to confine the plasma within the processing region, but also function to protect the internal structures of the processing chamber, including the chamber walls.

[0004] The integrity of features formed on the substrate surface depends on uniform plasma density within the processing region. Plasma uniformity can be tuned by adjusting the shape of the confinement rings (e.g., C-shrouds) to increase the volume of the processing region. However, changing the shape or structure of the confinement rings to increase their volume may require significant modifications to, for example, the hardware used within the processing chamber (e.g., processing chamber spacer plates, bonding hardware, etc.). Alternatively, changes to the structure of the confinement rings may result in a loss of mechanical strength or a shortened lifespan of the confinement rings.

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

[0006] Various embodiments of the present invention provide a confinement ring structure for use in a plasma processing chamber to confine plasma within a plasma region. The confinement ring is defined to include an upper horizontal portion extending between an outer radius and an upper inner radius, a lower horizontal portion extending between an outer radius and a lower inner radius, and a vertical portion extending between a bottom surface of the upper horizontal portion and an upper surface of the lower horizontal portion defined at the outer radius. The upper surface of the lower horizontal portion of the confinement ring is defined by a slope defined at an angle along the upper surface that descends toward the lower inner radius. The slope creates a thickness difference in the lower horizontal portion, with the thickness of the lower horizontal portion near the inner radius of the confinement ring being greater than the thickness of the lower horizontal portion at the lower inner radius. In some embodiments, the bottom surface of the lower horizontal portion is defined to be flat. Alternatively, in addition to defining a slope on the top surface, a second slope is defined along the bottom surface of the lower horizontal portion. The second slope is formed by a second angle provided along the bottom that descends toward the lower inner radius. The second slope at the bottom may be defined by adding additional material to the confinement ring. In some embodiments, forming a second slope along the bottom surface of the lower horizontal section results in a thickness of the lower horizontal section near the inner radius that is equal to the thickness of the lower horizontal section at the lower inner radius. In another embodiment, forming a second slope along the bottom surface of the lower horizontal section may result in a thickness of the lower horizontal section near the inner radius that is different from the thickness of the lower horizontal section near the lower inner radius. Improving the shape of the confinement ring by providing a sloped shape on the lower horizontal section helps to adjust plasma uniformity within the plasma region without requiring redesign of other hardware components of the plasma processing chamber. Furthermore, improvements made to the lower horizontal section (e.g., defining sloped surfaces along both the top and bottom surfaces of the lower horizontal section) avoid adversely affecting the mechanical strength or lifespan of the consumable confinement ring.

[0007] The lower horizontal section includes a plurality of slots defined along its length. Each slot extends radially from the inner diameter to the outer diameter along the lower horizontal section and vertically between the top and bottom surfaces of the lower horizontal section. The slots are used to remove by-products and neutral gases generated in the plasma region while ensuring optimal plasma confinement within the plasma region. In some embodiments, each slot may be defined with a parallel slot shape, where an inner slot radius defined at the inner diameter is equal to an outer slot radius defined at the outer diameter. In another embodiment, in addition to the angled shape on the lower horizontal section, the slots are defined using a tapered slot shape. A tapered slot shape is beneficial because the slots experience differential wear along their length due to constant exposure to the plasma. The tapered slot shape helps to optimally handle the limited space between the slots while improving the useful life of the confinement ring.

[0008] For example, slot wear is greater at the inner diameter than at the outer diameter. This uneven wear can be attributed to differences in plasma volume near the inner diameter relative to the outer diameter of the slot. When wear reaches a critical dimension, the confinement ring needs to be replaced to ensure plasma unconfinedness does not occur. A tapered slot shape helps address uneven wear while extending the life of the confinement ring. The tapered slot shape efficiently utilizes the area around the slot by defining a narrow end at the inner diameter and a wide end at the outer diameter. The tapered shape allows the narrow end of the slot to approach the critical dimension at approximately the same time as the wide end of the slot, resulting in the entire slot length reaching the critical confinement dimension at the end of its life. By efficiently utilizing the area around the slot, especially at the outer diameter, the tapered slot shape extends the useful life of the confinement ring while maintaining optimal plasma confinement within the plasma region. As a result, the number of processing cycles that the confinement ring can be used in a plasma processing chamber increases, thereby reducing costs associated with consumable confinement rings. Therefore, the original life expectancy of the confinement rings is maintained (i.e., the life of the confinement rings is not compromised) by the improvements to the confinement ring structure (i.e., including the tapered slot shape and the sloped lower horizontal section) without requiring redesign of other hardware components of the plasma processing chamber.

[0009] In one embodiment, a confinement ring for use in a plasma processing chamber is disclosed. The confinement ring comprises an upper horizontal portion, a lower horizontal portion, and a vertical portion. The upper horizontal portion extends between an upper inner radius and an outer radius of the confinement ring. The lower horizontal portion extends between a lower inner radius and an outer radius of the confinement ring. An upper surface of the lower horizontal portion provides an angle that descends toward the lower inner radius, the angle defining a slope along the upper surface. The lower horizontal portion includes an extension that extends downward along the lower inner radius. The vertical portion is disposed between the outer radius and the inner radius of the confinement ring. The vertical portion connects the upper horizontal portion to the lower horizontal portion of the confinement ring.

[0010] In one embodiment, the bottom surface of the lower horizontal portion is flat such that a first thickness of the lower horizontal portion near the inner radius is greater than a second thickness of the lower horizontal portion at the lower inner radius.

[0011] In one embodiment, the first thickness is between about 10% and about 40% greater than the second thickness.

[0012] In one embodiment, the angle defines a slope along the upper surface of the lower horizontal section, the slope being defined to be between about 0.20° and about 1° as measured from the horizontal x-axis.

[0013] In one embodiment, the bottom surface of the lower horizontal section presents a second angle that slopes downward toward the lower inner radius. The second angle defines a second slope. The second angle of the second slope defined on the bottom surface of the lower horizontal section is equal to the angle of the slope defined on the top surface of the lower horizontal section such that the first thickness of the lower horizontal section near the inner radius is equal to the second thickness of the lower horizontal section defined at the lower inner radius.

[0014] In one embodiment, a first height defined between the bottom surface of the upper horizontal section and the top surface of the lower horizontal section near the inner radius is less than a second height defined between the bottom surface of the upper horizontal section and the top surface of the lower horizontal section at a lower inner radius of the confinement ring.

[0015] In one embodiment, the lower horizontal section, the upper horizontal section, and the vertical section are integrally connected to define a C-shaped structure configured to confine a plasma generated in a plasma processing chamber.

[0016] In one embodiment, the lower horizontal portion comprises a plurality of slots, each of which extends radially along the lower horizontal portion from the inner diameter to the outer diameter, with the inner slot radius at the inner diameter of each slot being equal to the outer slot radius at the outer diameter.

[0017] In one embodiment, the inner diameter of the slot is greater than the inner ring diameter defined by the lower inner radius, and the outer diameter of the slot is less than the outer ring diameter defined by the outer diameter of the confinement ring.

[0018] In one embodiment, the lower horizontal portion includes a plurality of slots, each of which extends radially along the lower horizontal portion from the inner diameter to the outer diameter, with an inner slot radius at the inner diameter of each slot being smaller than an outer slot radius at the outer diameter.

[0019] In one embodiment, the difference between the inner and outer slot radii of each slot defines a slot taper such that each slot tapers from the outer diameter to the inner diameter. The inner and outer slot radii that affect the slot taper are sized to be the reciprocal of the wear rates at the corresponding inner and outer diameters of the slot. The ratio of inner slot radius to outer slot radius is about 1:1.1 to about 1:1.5.

[0020] In one embodiment, the upper inner radius is greater than the lower inner radius of the confinement rings.

[0021] In one embodiment, the extension defined in the lower horizontal portion extends vertically downward at the lower inner radius.

[0022] In one embodiment, the extension defined on the lower horizontal section is defined by an angled top and a vertical bottom, the angled top providing a third angle down at a downwardly sloping point defined on the upper surface of the lower horizontal section at the lower inner radius, and the vertical bottom extending downwardly from the bottom of the angled top.

[0023] In one embodiment, the top surface of the upper horizontal portion comprises a plurality of holes, each hole configured to receive a portion of a fastening means defined on a bottom surface of the upper electrode for coupling the confinement ring to the upper electrode of the plasma processing chamber.

[0024] In one embodiment, the extension of the lower horizontal section is configured to rest on a radio frequency gasket defined on an upper surface of a lower electrode of a plasma processing chamber.

[0025] In another embodiment, a confinement ring for use in a plasma processing chamber is disclosed. The confinement ring comprises an upper horizontal portion, a lower horizontal portion, and a vertical portion. The upper horizontal portion extends between an upper inner radius and an outer radius of the confinement ring. The lower horizontal portion extends between a lower inner radius and an outer radius of the confinement ring. The upper surface of the lower horizontal portion presents a first angle that descends toward the lower inner radius to define a first slope along the upper surface. The bottom surface of the lower horizontal portion presents a second angle that descends toward the lower inner radius to define a second slope along the bottom surface. The lower horizontal portion includes an extension that extends downward along the lower inner radius. The vertical portion is disposed between the outer radius and the inner radius of the confinement ring. The vertical portion connects the upper horizontal portion to the lower horizontal portion of the confinement ring.

[0026] In one embodiment, the first angle of the first slope is equal to the second angle of the second slope.

[0027] In one embodiment, a first thickness of the lower horizontal portion near the inner radius is equal to a second thickness of the lower horizontal portion at the lower inner radius, and a first height defined between a bottom surface of the upper horizontal portion and a top surface of the lower horizontal portion near the inner radius is less than a second height defined between the bottom surface of the upper horizontal portion and a top surface of the lower horizontal portion at the lower inner radius.

[0028] In one embodiment, the lower horizontal portion includes a plurality of slots, each of which extends radially from an inner diameter to an outer diameter along the lower horizontal portion. An inner slot radius at the inner diameter of each slot is equal to an outer slot radius at the outer diameter of each slot. The inner diameter of each slot is greater than an inner ring diameter of the confinement ring defined by the lower inner radius, and the outer diameter of the slot is less than an outer ring diameter of the confinement ring defined by the outer radius.

[0029] In one embodiment, the lower horizontal portion comprises a plurality of slots, each of which extends radially along the lower horizontal portion from the inner diameter to the outer diameter, with an inner slot radius of each slot at the inner diameter being smaller than an outer slot radius at the outer diameter.

[0030] In yet another embodiment, a plasma processing chamber for confining a plasma therein is disclosed. The plasma processing chamber includes a lower electrode for supporting a substrate and an upper electrode disposed above the lower electrode. The plasma processing chamber includes a confinement ring disposed between the lower electrode and the upper electrode. The confinement ring includes an upper horizontal portion, a lower horizontal portion, and a vertical portion. The upper horizontal portion extends between an upper inner radius and an outer radius of the confinement ring. The lower horizontal portion extends between a lower inner radius and an outer radius of the confinement ring. An upper surface of the lower horizontal portion provides an angle that descends toward the lower inner radius. The angle defines a slope along the upper surface. The lower horizontal portion has an extension that extends downward along the lower inner radius. The vertical portion is disposed between the outer radius and the inner radius of the confinement ring. The vertical portion connects the upper and lower horizontal portions of the confinement ring.

[0031] In one embodiment, the bottom surface of the lower horizontal section presents a second angle that descends toward the lower inner radius. The second angle defines a second slope along the bottom surface. The second angle of the second slope defined along the bottom surface is equal to the angle of the slope defined on the upper surface of the lower horizontal section.

[0032] In one embodiment, the lower horizontal portion comprises a plurality of slots, each slot of the plurality of slots configured to extend radially along the lower horizontal portion from the inner diameter to the outer diameter, with an inner slot radius of each slot at the inner diameter being smaller than an outer slot radius of each slot at the outer diameter.

[0033] In one embodiment, the inner diameter of each slot is greater than an inner ring diameter defined by the lower inner radius of the confinement ring, and the outer diameter of the slot is less than an outer ring diameter defined by the outer radius of the confinement ring.

[0034] In one embodiment, the upper inner radius is greater than the lower inner radius of the confinement rings.

[0035] In one embodiment, the lower horizontal section, vertical section, and upper horizontal section of the confinement ring define a continuous C-shaped structure for confining plasma to a plasma region defined in the plasma processing chamber, and the confinement ring is made from one of silicon, polysilicon, silicon carbide, boron carbide, ceramic, and aluminum.

[0036] In one embodiment, the extension is integral with the lower horizontal section, the vertical section, and the upper horizontal section of the confinement ring, and is configured to extend vertically below a bottom surface of the lower horizontal section.

[0037] In one embodiment, the upper electrode is electrically grounded and the lower electrode is connected to a radio frequency power source through a corresponding matching network. [Brief explanation of the drawings]

[0038] [Figure 1] 2 is an enlarged vertical cross-sectional view of a portion of a plasma processing chamber employing confinement rings having a tapered shape defined along the top surface of the lower horizontal section, according to one embodiment.

[0039] [Figure 2A] 1 illustrates an exemplary confinement ring having a tapered shape defined along an upper surface of a lower horizontal section, according to one embodiment.

[0040] [Figure 2B] 2B is another embodiment of the confinement ring shown in FIG. 2A with tapered shapes defined on both the top and bottom surfaces of the lower horizontal section of the confinement ring.

[0041] [Figure 2C] 2B is another embodiment of the confinement ring shown in FIG. 2A, in which the top of the extension has a straight shape.

[0042] [Figure 3] 1 is a representative graph of plasma density variation corresponding to oxide blanket etch rate across the radius of a substrate surface (when a substrate is present), according to one embodiment.

[0043] [Figure 4A] 1B is a close-up view of a portion of a confinement ring having a tapered shape along an upper surface of the lower horizontal portion and a plurality of slots with parallel slot shapes defined along the lower horizontal portion, according to one embodiment.

[0044] [Figure 4B] 4B is another embodiment of the confinement ring shown in FIG. 4A, having a tapered shape along the top and bottom surfaces of the lower horizontal portion of the confinement ring, and having a plurality of tapered slots defined along the lower horizontal portion.

[0045] [Figure 5A] 10 is a close-up view of a tapered slot defined along a bottom horizontal portion of a confinement ring, according to one embodiment.

[0046] [Figure 5B] 10A-10C illustrate close-up views of a tapered slot profile at the start and a worn slot profile at the end of the life of a containment ring, according to one embodiment.

[0047] [Figure 6] 1 illustrates a top perspective view of a confinement ring according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0048] In various embodiments described herein, a confinement ring for use in a plasma processing chamber is configured to enhance the service life of the confinement ring while ensuring optimal plasma sealing within a plasma region defined in the plasma processing chamber. The confinement ring for use in the plasma processing chamber includes an upper horizontal portion, a vertical portion, and a lower horizontal portion. The upper horizontal portion is defined to extend from an outer radius to an upper inner radius, and the top and bottom surfaces of the upper horizontal portion are flat. The lower horizontal portion is defined to extend from the outer radius to the lower inner radius. The vertical portion is disposed between the outer and inner radii of the confinement ring and connects the upper horizontal portion to the lower horizontal portion of the confinement ring. The upper surface of the lower horizontal portion is tapered to define a slope that slopes downward toward the lower inner radius. The slope defined on the upper surface results in a difference in thickness of the lower horizontal portion of the confinement ring near the inner radius and the lower inner radius. Additionally, the slope results in a difference in height of a gap defined between the bottom of the upper horizontal portion and the top of the lower horizontal portion near the inner radius and at the lower inner radius. The height difference results in an increase in the volume of plasma generated in the plasma region, particularly in the region covered by the confinement rings (e.g., above the edge region of the substrate when the substrate is in the plasma processing chamber and above the edge ring surrounding the substrate).

[0049] Increasing the gap in the confinement rings has a positive effect on plasma uniformity. Plasma uniformity may be due to changes in plasma diffusion due to increased volume within the plasma region. Thus, plasma uniformity can be adjusted by changing the shape of the confinement rings used to confine the plasma to the plasma region without requiring redesign of other hardware components of the plasma processing chamber. Existing methods for modifying the conventional design of confinement rings require significant modifications to the hardware or result in a loss of mechanical strength and consequent loss of life of the confinement rings.

[0050] Selective modifications are made to the confinement ring (e.g., including a slope along the lower horizontal portion of the confinement ring) to increase the plasma volume. The modifications made to the confinement ring structure do not substantially deviate from the overall structure of the confinement ring and therefore do not require modifications to other hardware components in the plasma processing chamber (e.g., chamber spacer plates, bonding hardware, etc.). In some embodiments, a further improvement by providing a slope may be made to the bottom surface of the lower horizontal portion to improve the mechanical strength and overall lifespan of the confinement ring. The slope may be defined at the bottom surface by adding additional material to the confinement ring along the length of the bottom to provide a downward angle toward the lower inner radius. The additional material at the bottom surface is configured to increase the thickness of the lower horizontal portion to provide overall thickness uniformity along the length of the lower horizontal portion while continuing to maintain the slope in the lower horizontal portion.

[0051] The lower horizontal section includes multiple slots for efficiently removing by-products from the plasma region while protecting the plasma seal within the plasma region. The slots are defined to extend longitudinally from the inner diameter to the outer diameter along the lower horizontal section and in a depth direction between the top and bottom surfaces of the lower horizontal section to provide conduits for by-product exhaust from the plasma region. In some embodiments, the slots may be defined to have a parallel slot shape along their length, with the inner slot radius at the inner diameter being the same as the outer slot radius at the outer diameter. In other embodiments, the slots may be defined to have a tapered slot shape that is narrow at the inner diameter and wide at the outer diameter. The wider side at the outer diameter has the wider outer slot radius, and the narrower side at the inner diameter has the narrower inner slot radius. The inner slot radius at the inner diameter and the outer slot radius at the outer diameter of each slot are sized to be the reciprocal of the wear rate at the corresponding inner and outer diameters. Starting with a narrow slot at the inner diameter allows more wear to occur at the inner diameter before reaching the critical dimension of plasma non-sealing. At the end of its useful life, the small inner slot radius on the inner diameter offsets the high wear rate on the inner diameter, and the wide outer slot radius offsets the low wear rate on the outer diameter, resulting in a straight slot shape along the length of the slot. The difference between the inner and outer slot radii causes each slot to reach its sealing limit simultaneously along the entire slot length. Tapered slots may provide some open area along the narrow side. To compensate for the open area along the narrow side, the total number of slots may be increased. The increase in the total number of slots accounts for the expected amount of wear along the narrow side of the tapered slot.

[0052] The improved confinement ring structure, having a sloped profile along the length of the lower horizontal section and a tapered slot profile of the plurality of slots defined along the length of the lower horizontal section, provides (a) an overall improvement in plasma uniformity, (b) efficient removal of by-products, and (c) an overall improvement in confinement ring lifetime. The foregoing advantages are achieved without requiring redesign of other hardware components (e.g., chamber spacer plates, bonding hardware, etc.) within the plasma processing chamber. In response to the foregoing summary of the invention, specific embodiments are described below with reference to the various figures.

[0053] 1 illustrates a simplified block diagram of a portion of a plasma processing chamber 100 that, in one embodiment, uses confinement rings to confine the plasma. In one embodiment, the plasma processing chamber 100 may be a capacitively coupled plasma (CCP) processing chamber (or simply, hereinafter referred to as "plasma processing chamber") that includes a lower electrode 104 for providing radio frequency (RF) power to the plasma processing chamber 100 and an upper electrode 102 for providing a process gas to generate a plasma within 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 generators (not shown).

[0054] In one embodiment, the upper surface of the lower electrode 104 defines a substrate support surface on which a substrate 110 is received for processing. 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. The upper surface of the edge ring 112 is defined to be coplanar with the upper surface of the substrate 110 when the substrate is supported on the substrate support surface of the lower electrode 104. The edge ring 112 is configured to expand the processing region (plasma region 108) for plasma generated in the plasma processing chamber 100 beyond the broad processing region extending beyond the edge of the substrate and covering the outer edge of the edge ring 112. One or more dielectric rings 120 are positioned adjacent the outer edge of the edge ring 112. An RF power source 106 is connected to the bottom of the lower electrode through a matching network 107 to provide RF power to the plasma processing chamber 100. The ground ring 122 is disposed below and adjacent to a portion of the one or more dielectric rings 120 and is configured to surround the lower electrode 104. The support structure 118 is disposed to surround a portion of the ground ring 122 of the lower electrode 104. The RF gasket 116 is disposed on an upper surface of the support structure 118. In some embodiments, the RF gasket 116 may be disposed within a flow path defined in the upper surface of the support structure 118. The support structure 118 may be made of a quartz element or other insulating material suitable for use in the plasma processing chamber 100.

[0055] In one embodiment, the upper electrode 102 may be a showerhead including one or more inlets (not shown) connected to one or more process gas sources (not shown) and multiple outlets distributed on a bottom surface of the upper electrode 102 facing the lower electrode 104. The multiple outlets are configured to deliver process gases 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 102 and the lower electrode 104. The upper electrode 102 may be composed of multiple electrodes. FIG. 1 illustrates one such embodiment, in which the upper electrode 102 includes a centrally located inner upper electrode 102a and an outer electrode 102b positioned adjacent to and surrounding the inner upper electrode 102a. In this embodiment, the upper electrode 102 is electrically grounded to provide a ground return path for the RF power supplied to the plasma processing chamber 100a. The outer electrode 102b includes multiple fasteners (not shown) disposed along its bottom surface. A fastening means is used to couple the upper electrode 102 to the confinement rings 140 .

[0056] The confinement ring structure (or simply referred to hereinafter as "confinement ring") 140 is disposed between the upper electrode 102 and the lower electrode 104. The confinement ring 140 defines a sealed chamber space in which plasma generated in the chamber is sufficiently contained. The sealed chamber space defines the plasma region 108. The confinement ring 140 is a C-shaped structure, with the opening of the C facing inward toward the plasma region 108 defined between the upper electrode 102 and the lower electrode 104 of the processing chamber 100. Due to the shape of the confinement ring 140 and its function of confining the plasma to a region, the confinement ring may also be referred to as a "C-shroud." The confinement ring 140 is used to confine plasma to a large plasma region 108 in the plasma processing chamber 100. The confinement ring 140 is configured such that its upper portion is coupled to the outer electrode 102b, which is part of the upper electrode 102. The confinement rings 140 are part of the upper electrode 102, and the bottom of the confinement rings 140 are configured to rest on the top surface of the support structure 118 of the lower electrode 104. An RF gasket 116 is provided on the top surface of the support structure 118 to provide a strong coupling between the upper electrode 102 and the lower electrode 104 when the plasma processing chamber 100 is engaged in processing. The RF gasket 116 ensures an air coupling between the upper electrode 102 and the lower electrode 104. In one embodiment, the support structure 118 is configured to surround a region of the lower electrode 104 that includes at least the substrate support surface, the edge ring 112, the one or more dielectric rings 120, and the ground ring 122.

[0057] It should be noted that while the plasma processing chamber in Figure 1 is shown with only certain components, in reality, a plasma processing chamber will include multiple additional components necessary for substrate processing. Furthermore, the various components shown in Figure 1 may not be drawn to scale and / or may be exaggerated in order to distinguish their different features.

[0058] Generally, the confinement ring 140 comprises an upper horizontal portion 141, a vertical portion 142, and a lower horizontal portion 143. The upper horizontal portion 141 extends a first length and is defined by a bottom surface 141a facing the plasma region 108 and a top surface 141b facing the opposite side of the plasma region 108. A plurality of holes are distributed throughout the top surface 141b to receive fastening means defined on the bottom surface of the outer electrode 102b when coupling the confinement ring 140 to the upper electrode 102. In one embodiment, the bottom surface 141a and the top surface 141b of the upper horizontal portion 141 are substantially flat (i.e., horizontal). In another embodiment, a first step 148a is defined in the top surface 141b of the upper horizontal portion 141 at an inner end of the upper horizontal portion 141. The first step may be used to receive the outer electrode 102b and provide a secure connection of the confinement ring 140 when coupling the confinement ring 140 to the outer electrode 102b. In this embodiment, the bottom surface 141a of the upper horizontal portion 141 is substantially flat. In yet another embodiment, the first step 148a is defined on the top surface 141b of the upper horizontal portion 141, and the second step 148b is defined on the bottom surface 141a of the upper horizontal portion 141 at an inner end of the upper horizontal portion 141. In this embodiment, the first step 148a and the second step 148b both extend in height. In another embodiment, the first step 148a may extend a first height, and the second step 148b may extend a second height. In another embodiment, the bottom surface 141a of the upper horizontal portion 141 provides an angle that rises toward the upper inner radius 151 to define a slope along the upper horizontal portion. In one example, the inclination angle of the bottom surface of the upper horizontal portion may be defined as greater than 0° and less than 1°, although other inclination ranges may be envisioned.

[0059] The vertical portion 142 includes an inner surface 142a facing the plasma region 108 and an outer surface 142b facing away from the plasma region 108 and toward the inside of the wall of the processing chamber 100. In one embodiment, the inner surface 142a and the outer surface 142b of the vertical portion 142 are vertical. FIG. 1 shows an example in which the inner surface 142a and the outer surface 142b of such a vertical portion 142 are vertical. In another embodiment, the inner surface 142a of the vertical portion 142 is curved, and the outer surface 142b of the vertical portion 142 is vertical. In yet another embodiment, both the inner surface 142a and the outer surface 142b of the vertical portion 142 are curved.

[0060] The lower horizontal portion 143 extends a second length and is defined by a top surface 143a facing the plasma region 108 and a bottom surface 143b facing the opposite side of the plasma region 108. The top surface 143a of the lower horizontal portion 143 slopes downward from the vertical portion toward the inner edge of the lower horizontal portion 143. The slope of the lower horizontal portion 143 creates a change in the height of the gap defined between the upper horizontal portion 141 and the lower horizontal portion 143. In some embodiments, a first height "h1" defined between the upper horizontal portion 141 and the lower horizontal portion 143 near the vertical portion 142 is less than a second height "h2" defined between the upper horizontal portion 141 and the lower horizontal portion 143 near the inner edge of the lower horizontal portion 143. The lower horizontal portion 143 also includes an extension 144 disposed at the inner edge of the lower horizontal portion 143 and extending downward from the bottom surface 143b of the lower horizontal portion 143. In one embodiment shown in FIG. 1, extension 144 has a straight inner surface.

[0061] In one embodiment, the upper horizontal portion 141, the vertical portion 142, and the lower horizontal portion 143 may be integrally connected to define a C-shaped structure. In another embodiment, the upper horizontal portion 141, the vertical portion 142, and the lower horizontal portion 143 may be three separate elements, configured such that the bottom surface of the upper horizontal portion 141 rests on and is coupled to the top surface of the vertical portion 142. The bottom surface of the vertical portion 142 rests on and is coupled to the top surface 143a of the lower horizontal portion 143. The upper horizontal portion 141, the vertical portion 142, and the lower horizontal portion together form a C-shaped structure for confining plasma generated in the plasma processing chamber 100 to the plasma region 108.

[0062] FIG. 2A depicts an enlarged cross-sectional view of a confinement ring 140 used in one embodiment with the plasma processing chamber 100. The view in FIG. 2A identifies various reference points on the confinement ring 140. As described above, the confinement ring 140 is a C-shaped structure and includes an upper horizontal portion 141, a vertical portion 142, a lower horizontal portion 143, and an extension portion 144. The upper horizontal portion 141 extends between an outer radius 150 and an upper inner radius 151 of the confinement ring 140 and includes a bottom surface 141 a and a top surface 141 b. The bottom surface 141 a and the top surface 141 b of the upper horizontal portion 141 may or may not include a step at the upper inner radius 151. The bottom surface 141 a faces the plasma region 108, and the top surface 141 b faces the opposite side of the plasma region 108. The top surface 141b of the upper horizontal portion 141 includes a plurality of fastener holes (or simply referred to as "holes") (not shown) uniformly distributed in a circular orientation and defined to align with corresponding fastener means disposed along the bottom surface of the outer electrode 102b. The fastener means of the outer electrode 102b and the fastener holes in the top surface 141b of the outer electrode 102b are defined to couple the confinement ring 140 to the upper electrode 102.

[0063] The vertical portion 142 of the confinement ring 140 is disposed between the outer radius 150 and the inner radius 153 of the confinement ring. The vertical portion 142 includes an inner surface 142a facing the inside of the plasma region 108 and an outer surface 142b facing the opposite side of the plasma region 108. Either or both of the inner surface 142a and the outer surface 142b of the vertical portion 142 may be vertical or curved. The vertical portion extends between the upper horizontal portion 141 and the lower horizontal portion 143 at a height that defines a gap in which the plasma is confined. In some embodiments, the vertical portion 142 joins the upper horizontal portion 141 to the lower horizontal portion 143 to define a C-shaped structure.

[0064] The lower horizontal portion 143 extends between an outer radius 150 and a lower inner radius 152 of the confinement ring 140. In one embodiment, the lower inner radius 152 of the confinement ring 140 is smaller than the upper inner radius 151 of the confinement ring 140. The lower horizontal portion includes a top surface 143a and a bottom surface 143b. The top surface 143a of the lower horizontal portion 143 is angled downward toward the lower inner radius 152, while the bottom surface 143b of the lower horizontal portion 143 is flat. This angle defines a slope along the top surface 143a of the lower horizontal portion 143. In one embodiment, the slope begins near the inner radius 153 of the confinement ring and extends toward the lower inner radius 152. The sloped top surface 143a and flat bottom surface 143b result in a change in thickness along the length of the lower horizontal portion 143. For example, the slope along the upper surface 143a causes the lower horizontal portion 143 to have a first thickness "T1" near the inner radius 153 of the confinement ring 140 and a second thickness "T2" near the lower inner radius 152 of the confinement ring 140 (T1 > T2). In one embodiment, the first thickness T1 is defined to be about 10% to about 40% greater than the second thickness T2. Furthermore, the thickness variation results in a variation in the height of the gap defining the plasma region 108 defined between the bottom surface 141a of the upper horizontal portion 141 and the top surface 143a of the lower horizontal portion 143. For example, the slope results in a first height "h1" defined near the inner radius of the confinement ring 140 and a second height "h2" defined near the lower inner radius 152, where the first height h1 is less than the second height h2.

[0065] In one embodiment, the slope angle 147 defined by the slope of the lower horizontal portion 143 relative to the horizontal x-axis may be defined to be between about 0.20° and about 1°. The aforementioned range of slope angles is provided by way of example only and should not be considered limiting. As a result, in some embodiments, the slope angle may be greater or less than that range, and such an increase or decrease may be based on the inner diameter of the plasma processing chamber 100, the type of process being performed, the type of process gas used to generate the plasma, the types of by-product and neutral gas species to be generated and subsequently removed, the access openings of the plasma processing chamber, etc. In one embodiment, the confinement rings are made of silicon. In other embodiments, the confinement rings may be made of polysilicon, silicon carbide, boron carbide, ceramic, aluminum, or other materials capable of withstanding the processing conditions of the plasma region 108.

[0066] Lower horizontal portion 143 includes an extension 144' defined by lower inner radius 152. In the embodiment shown in FIG. 2A, extension 144' includes an angled top portion 144a and a vertical bottom portion 144b. This extension 144 configuration differs from the configuration used in FIG. 1 in that extension 144 in FIG. 1 has a straight inner surface, while extension 144' in FIG. 2A has a sloped portion at its top. Angled top portion 144a, defined by downward slope point 149, slopes at an angle, and downward slope point 149 is defined at the intersection of upper surface 143a and the inner surface of lower inner radius 152. The slope angle of angled top portion 144a can be from about 0° to about 10°. The foregoing ranges are provided by way of example and should not be considered limiting or comprehensive. Vertical bottom portion 144b is disposed below angled top portion 144a and extends vertically downward to a height that exceeds bottom surface 143b of lower horizontal portion 143. Extension portion 144' provides continuity to lower horizontal portion 143. Vertical bottom portion 144b is configured to rest on RF gasket 116 that is disposed on the upper surface of support structure 118 defined by lower electrode 104.

[0067] FIG. 2B illustrates a variation of the configuration of the confinement ring 140 shown in FIG. 2A , in one embodiment. The confinement ring 140′ of FIG. 2B includes a second slope defined along the bottom surface 143b of the lower horizontal portion 143 in addition to the slope defined on the top surface 143a of the lower horizontal portion 143 of the confinement ring 140. Various components of the confinement ring 140 common to both FIG. 2A and FIG. 2B are designated with the same reference numerals and function similarly. The bottom surface 143b of the lower horizontal portion 143 provides a second angle that descends toward the lower inner radius 152, defining a second slope along the bottom surface 143b of the lower horizontal portion 143. Similar to the slope in the embodiment of FIG. 2A , the second slope begins near the inner radius 153 of the confinement ring and extends toward the lower inner radius 152. In one embodiment, the second angle of the second slope defined along the bottom surface 143b of the lower horizontal portion 143 is equal to the slope angle defined along the top surface 143a of the lower horizontal portion 143. For example, the second slope is defined to be between about 0.20° and about 1°. In this embodiment, the thickness of the lower horizontal portion 143 is uniform along the length of the lower horizontal portion 143.

[0068] In another embodiment, the second angle of the second slope defined along the bottom surface 143b may be different from the slope defined along the top surface 143a. For example, the second angle of the second slope may be greater than the slope angle along the top surface 143a, resulting in a change in thickness along the length of the lower horizontal portion 143. In this embodiment, the thickness T1 near the inner radius 153 may be less than the thickness T2 near the lower inner radius 152. This embodiment is a variation of the embodiment shown in FIG. 2A , in which the thickness varies along the length of the lower horizontal portion 143. For example, the thickness T1 near the inner radius 153 is less than the thickness T2 near the lower inner radius 152, whereas in the embodiment of FIG. 2A , the thickness T1 near the inner radius 153 is greater than the thickness T2 near the lower inner radius 152. This may be to account for additional wear expected at the lower inner radius 152 due to exposure to plasma in the plasma region 108.

[0069] FIG. 2C depicts another embodiment of the confinement ring 140 depicted in FIG. 2A. In this embodiment, the extension 144 is defined by a top portion 144a' and a vertical bottom portion 144b. The top portion 144a' is shown to have a straight shape along an inner surface disposed at the lower inner radius 152, rather than the angled top portion depicted in FIG. 2A. In the embodiment depicted in FIG. 2C, the top portion 144a' extends down at the lower inner radius 152 to the bottom surface 143b of the lower horizontal portion 143, and the vertical bottom portion 144b is an extension of the top portion 144a'. The vertical bottom portion 144b extends below the bottom surface 143b of the lower horizontal portion 143 of the confinement ring 140.

[0070] The embodiment shown in Figures 2A-2C illustrates a vertical cross-section of a confinement ring 140 with a slope defined along the top surface 143a and along both the top surface 143a and the bottom surface 143b. The cross-sections in Figures 2A and 2B also illustrate slots 145 defined along the length of the lower horizontal portion 143 of the confinement ring 140. The confinement ring 140 includes a plurality of slots uniformly distributed along the lower horizontal portion 143 of the confinement ring 140, each extending lengthwise between the inner and outer diameters and depthwise between the top surface 143a and the bottom surface 143b of the lower horizontal portion. Details regarding the slot geometry are described with reference to Figures 4A and 4B. The plurality of slots 145 defined along the lower horizontal portion 143 optimally confines the plasma to the plasma region while providing conduits for evacuating by-products from the plasma region.

[0071] FIG. 3 illustrates a graph identifying the change in etch rate due to changes in plasma density across the radius of a substrate when confinement rings having a sloped profile defined along the lower horizontal portion 143 are used, according to one embodiment. The graph shows the blanket oxide etch rate on the surface of a substrate processed using confinement rings having a sloped profile as described in various embodiments. The blanket etch rate indicates the appropriate degree of plasma density above the substrate surface. Graph line 301 illustrates the change in etch rate on the substrate surface when non-sloped confinement rings are used, while graph line 302 illustrates the change in etch rate on the substrate surface when confinement rings having a slope defined along the lower horizontal portion 143 are used. The etch rate depicted along graph line 301 shows more variation along the length of the substrate, leading up to the edge region defined by line 304. The change in etch rate is more pronounced on graph line 301 for radii between about 70 mm and about 135 mm for a 150 mm substrate, as seen in box 303. For example, the etch rate exhibits a gradual decrease along the substrate surface up to the midpoint of the radius (i.e., up to about 70 mm), after which it begins to increase significantly up to the edge region of the substrate. Meanwhile, graph line 302 exhibits a more gradual decrease in etch rate along the length of the substrate surface up to the edge region. The gradual decrease in etch rate exhibited by graph line 302 is hypothesized to be due to changes in plasma diffusion in the increased plasma volume resulting from the increased gap defined between the upper and lower horizontal portions of confinement rings 140.

[0072] In one embodiment, the amount of slope along the lower horizontal portion may be defined to increase the first height "h1" and the second height "h2" (i.e., the gap defined between the wafer-side horizontal portion 141 and the lower horizontal portion 143) by approximately +2 mm to approximately +8 mm. The effect of such an increase on the blanket etch rate is particularly illustrated by graph line 302 within the region enclosed by box 303. By way of example, a slope of approximately 0.55° to approximately 0.60° defined along the upper surface 143a of the lower horizontal portion 143 results in a difference between the first height "h1" and the second height "h2" of approximately 0.60 mm to approximately 0.65 mm. In one embodiment, the upper inner radius 151 is defined to be approximately 203 mm (approximately 8 inches) to approximately 218.5 mm (approximately 8.6 inches). In one embodiment, the lower inner radius 152 is defined to be approximately 177 mm (approximately 7 inches) to approximately 198.5 mm (approximately 7.8 inches). In one embodiment, inner radius 153 is defined to be between about 9.8 inches (248 mm) and about 10.3 inches (262 mm). In one embodiment, outer radius is defined to be between about 10 inches (254 mm) and about 10.5 inches (267 mm). In one embodiment, slot 145 length is defined to be between about 1.9 inches (48 mm) and about 2.4 inches (61 mm). In one embodiment, lower horizontal portion 143a depth (i.e., thickness T1) is defined to be between about 0.25 inches (6 mm) and about 0.33 inches (8.4 mm). In one embodiment, lower horizontal portion 143a is defined to have a first height h1 between about 1.18 inches (29 mm) and about 1.22 inches (31 mm) and a second height h1 between about 1.22 inches (31 mm) and about 1.24 inches (32 mm). In one embodiment, the sloped thickness T2 of the lower horizontal portion 143a may be defined to be between about 5.8 mm (about 0.23 inches) and about 7.2 mm (about 0.28 inches). The above ranges for the various components of the confinement ring are provided by way of example only and should not be considered limiting.Other ranges or adjustments to the above ranges for various components may be envisioned based on the inner diameter of the plasma processing chamber 100, the type of process being performed, the type of process gas used to generate the plasma, the types of by-product and neutral gas species that are generated and then removed, the access openings in the plasma processing chamber, the geometry of the hardware components of the plasma processing chamber, etc.

[0073] 4A and 4B illustrate variations of a confinement ring 140 having multiple slots defined along the length of the lower horizontal portion 143 thereof, according to some exemplary embodiments. The multiple slots 145 along the length of the lower horizontal portion 143 are used to efficiently remove by-products formed within the plasma region 108 during processing of the substrate 110. In the exemplary embodiment shown in FIG. 4A , each slot 145 of the multiple slots is shown extending radially between an inner diameter (ID) 145a and an outer diameter (OD) 145b of the lower horizontal portion 143. The ID 145a of the slot 145 is larger than an inner ring diameter (IRD) of the lower horizontal portion 143, the IRD being defined by a lower inner radius 152 of the lower horizontal portion 143. The OD 145b of the slot 145 is defined to be larger than the ID 145a of the slot 145 but smaller than an outer ring diameter (ORD) of the confinement ring 140, the ORD being defined by an outer radius 150 of the confinement ring 140. That is, the slots 145 extend a length "l" (i.e., l=OD-ID) that is less than the width "w" (i.e., w=ORD-IRD) of the lower horizontal portion 143. Each slot 145 is defined using a parallel slot geometry, where an inner slot radius (ISR) 145c at the inner diameter (ID) 145a of the slot 145 is equal to an outer slot radius (OSR) 145d at the outer diameter (OD) 145b of the slot 145. Each slot 145 having a parallel slot geometry is defined to extend between the top surface 143a and the bottom surface 143b of the lower horizontal portion 143.

[0074] FIG. 4B illustrates another embodiment of slots 145′ defined along the surface of lower horizontal portion 143 of confinement ring 140″. In this embodiment, slots 145′ are defined using a tapered slot shape rather than the parallel slot shape used to define slots 145 in FIG. 4A. Similar to FIG. 4A, each slot 145′ extends from an inner diameter (ID) 145a to an outer diameter (OD) 145b. ID 145a is smaller than the inner diameter (IRD) of lower horizontal portion 143, with the IRD defined by lower inner radius 152. OD 145b is larger than the IRD but smaller than the outer diameter (ORD) of confinement ring 140″, with the ORD defined by outer radius 150. In this embodiment, each of the plurality of slots 145′ is defined using a tapered slot shape to provide a slot taper. The slot taper is formed by defining a narrow inner slot radius (ISR) 145c' at the ID 145a of the slot 145' and a wider outer slot radius (OSR) 145d' at the OD 145b of the slot 145'. The change in ISR 145c' and OSR 145d' causes each slot 145' to be narrow at the inner diameter ID 145a and wide at the outer diameter OD 145b. To compensate for the narrow ISR at the inner diameter ID 145a, in one embodiment, the length "l" of the slot 145' may be increased to provide sufficient area for by-products and neutral gas species to escape from the plasma region 108. In another embodiment, the number of slots 145' may be increased to compensate for the narrow ISR 145c' at the ID 145a, with the increased number of slots 145' corresponding to wear of the slots 145'.

[0075] The ISR 145c' and OSR 145d' of each slot 145' are sized to be the inverse of the wear rate at the corresponding inner and outer diameters (ID 145a and OD 145b) of the slot 145'. Wear along the length of the slot 145' is uneven due to the plasma exposure of different portions along the length of the slot 145', with the region of the slot 145' at the inner diameter wearing more than the region of the slot 145' at the outer diameter. Narrowing the slot at ID 145a will extend the life of the confinement ring by offsetting the onset of reaching a critical width when plasma escapes through the slot. At the same time, increasing the OD 145b of the slot ensures that there is no loss of gas conductance due to the narrow ID 145a. The tapered slot shape allows the wear of the slot 145' at ID 145a to reach a critical dimension at approximately the same time as the wear of the slot 145' at OD 145b. The magnitude of the ISR and OSR is defined so that the tapered slot geometry also allows for the removal of by-products and neutral gas species from the plasma region 108. The tapered geometry used to define the slots extends the useful life of the confinement rings 140'.

[0076] The slots 145 shown in FIG. 4A and the slots 145′ shown in FIG. 4B are not drawn to scale and are exaggerated to illustrate the slot shapes used to define the slots along the length of the lower horizontal portions 143 of the confinement rings 140 and 140′. In some embodiments in which the confinement ring 140 includes an angled top surface 143a and an angled bottom surface 143b along the length of the lower horizontal portion 143, the angle of the bottom surface is defined equal to the angle of the top surface to maintain the bottom surface parallel to the top surface. This configuration helps improve the mechanical strength of the confinement ring 140, thereby improving its service life. Further improvements in service life may be envisioned by using a tapered slot shape to define the slots along the lower horizontal portion 143 of the confinement ring 140. The tapered slot shape used to define the slots 145, together with the angled lower horizontal portion 143, results in maintaining an optimal plasma density in the plasma region 108 to provide an optimal etch rate across the substrate surface while ensuring that the wear of the slots along their length reaches a critical dimension at approximately the same time.

[0077] FIG. 5A depicts an example of a tapered slot shape used to define a slot 145' along a lower horizontal portion 143 of a confinement ring 140 used in a plasma processing chamber in one embodiment. FIG. 5A also shows the change in the slot shape of the slot 145' defined using a tapered slot shape with respect to the slot 145 defined using a parallel slot shape. The slot 145' having the tapered slot shape is shown by a red line, and the slot 145 having the parallel slot shape is shown by a gray line. As described above, the slot 145' is defined to extend between an inner diameter (ID) 145a and an outer diameter (OD) 145b along the horizontal plane of the lower horizontal portion 143, and the ID 145a of the slot 145' is greater than the ring inner diameter (IRD) defined by the lower inner radius 152 of the lower horizontal portion 143, and the OD 145b of the slot 145' is greater than the ID 145a but smaller than the ring outer diameter (ORD) of the confinement ring defined by the outer radius 150. The slot 145' (illustrated by a red line in FIG. 5A) has a wide slot width at the outer diameter (OD) defined by the outer slot radius (OSR) 145d' and a narrow slot width at the inner diameter (ID) defined by the inner slot radius (ISR) 145c' (i.e., ISR 145c' < OSR 145d'). Since the slots wear differently along the slot length, the tapered shape of the slot 145' provides more area at the inner diameter than at the outer diameter due to slot wear so that when the replacement of the confinement ring 140 becomes necessary, the tapered slot 145' can reach the limiting dimensions almost simultaneously as a whole. This is different from the slot 145 (illustrated by a gray line in FIG. 5A) defined using a parallel slot shape. The slot 145 having the parallel slot shape is defined with a uniform slot width along its length. That is, the inner slot width at the ID of the slot 145 defined by the ISR 145c is equal to the outer slot width at the OD 145b defined by the OSR 145d. The parallel slot shape causes non-uniform wear along the length of the slot 145, and the replacement of the entire confinement ring 140 will be required.

[0078] Thus, to prevent premature replacement of the confinement ring 140 and extend its useful life while ensuring that the mechanical strength of the confinement ring 140 is not compromised throughout its useful life, the confinement ring 140 may be configured with a lower horizontal portion 143 having a slope defined along both the top surface 143 a and the bottom surface 143 b, and a slot 145′ having a tapered slot shape. Adding a slope to the bottom surface 143 b of the lower horizontal portion 143 improves the mechanical strength of the confinement ring by keeping the bottom surface parallel to the angled top surface, particularly when the slope defined on the bottom surface 143 b is equal to the slope defined on the top surface 143 a. Altering the configuration of the confinement ring 140, such as defining a sloped and parallel-slot-shaped slot 145 along the top surface 143 a of the lower horizontal portion 143, or defining a sloped and tapered-slot-shaped slot 145′ along the top surface 143 a of the lower horizontal portion 143, may be envisioned to improve plasma density across the length of the substrate surface.

[0079] FIG. 5B illustrates an exemplary wear profile of a slot 145′ defined by a tapered slot shape, according to one embodiment. The starting profile of the slot 145′ is shown in the center by the thick red line, with the ISR 145c at the ID 145a being smaller than the OSR 145d at the OD 145b. As the confinement ring 145′ is exposed to plasma from the plasma region 108 during processing operations, regions along the length of the slot 145′ exhibit uneven wear, with the region near the inner diameter (ID) 145a exhibiting more wear than the region around the outer diameter (OD) 145b. Because the wear rate is higher at the narrow end of the slot 145′ near the inner diameter and lower at the wide end near the outer diameter of the slot 145′, the region near the wide end reaches its critical dimension limit more slowly than the region near the narrow end. Thus, the wide end of the slot 145′ can withstand the same amount of processing operations as the narrow end before reaching its critical dimension limit, thereby extending the useful life of the confinement ring 145′. 5B shows the end-of-life shape of tapered slot 145′ as an elongated rounded rectangle surrounding tapered slot 145′, with wear of the area along the length of the tapered slot reaching a critical dimension at approximately the same time that the confinement ring needs to be replaced to avoid the occurrence of a plasma unconfined event. For details regarding the use of a tapered slot shape to define slot 145′ along the lower horizontal portion 143 of the confinement ring, reference may be made to commonly owned, co-pending International Patent Application No. PCT / US20 / 053894, filed October 30, 2020, entitled “Wear Compensating Confinement Ring,” all of which are incorporated herein by reference.

[0080] In some embodiments, the slot taper defined by the wide slot dimension at the outer diameter OD 145b and the narrow slot dimension at the inner diameter ID 145a is sized to be the inverse of the wear rate. By sizing the slot taper as a function of wear rate, a high wear rate at the inner diameter ID 145a is offset by a low wear rate at the outer diameter OD 145b, resulting in a nearly straight slot shape at end-of-life. The slot width along the entire slot length reaches its sealing limit (i.e., critical dimension) at approximately the same time. The tapered shape more efficiently utilizes the area of ​​the outer diameter. Additional slots may be defined to compensate for the open area of ​​the lower horizontal section due to the reduced slot dimension at the inner diameter. The number of additional slots may be defined by considering the amount of wear space required for each slot to reach its critical dimension at the narrow and wide ends. The tapered slot shape extends the amount of wear a slot can withstand before reaching its unsealing limit, resulting in a longer service life and improved consumable costs.

[0081] FIG. 6 depicts a top perspective view of a confinement ring 140 used in the plasma processing chamber 100 to confine plasma to the plasma region 108. The confinement ring 140 is a C-shaped structure configured to be positioned along the periphery of the plasma region 108 to confine plasma to the plasma region 108, which extends above the substrate 110 received on a substrate support surface defined by the lower electrode, the edge ring 112, and one or more dielectric rings 120. The confinement ring 140 is a replaceable consumable part. The upper surface of the confinement ring includes a plurality of fastener holes 146 uniformly arranged in a circular orientation, which are configured to align with and receive fasteners defined along the bottom surface of the outer electrode 102b of the upper electrode 102. The confinement ring 140 depicted in FIG. 4 exhibits an angled slope defined along the upper surface 143a of its lower horizontal portion 143. To enable the confinement ring 140 to withstand further processing operations, an additional slope may be defined along the bottom surface 143b of the lower horizontal portion 143 to improve the plasma density along the length of the substrate and the mechanical strength of the confinement ring. The lower horizontal portion 143 may comprise slots with a parallel slot shape or a tapered slot shape. The tapered slot shape offers an additional advantage over the parallel slot shape in that it provides additional area for wear near the inner diameter rather than the outer diameter, improving the useful life of the confinement ring.

[0082] Advantages of the confinement rings described in various embodiments include improving plasma uniformity without adversely affecting other hardware components (e.g., chamber spacer plates, bonding hardware, etc.) or the mechanical strength or useful life of the confinement rings. Plasma uniformity is tailored by improving the shape of the confinement rings without affecting their strength or inherent life expectancy. This improves the cost of the consumable confinement rings because the confinement rings can withstand more processing operations before reaching critical dimension limits along the length of the lower horizontal section and slots. Other advantages will be envisioned by those skilled in the art upon reviewing the various embodiments described herein.

Claims

1. 1. A confinement ring for use in a plasma processing chamber, comprising: an upper horizontal portion extending between an upper inner radius and an upper outer radius of the confinement ring; a lower horizontal portion extending between a lower inner radius and the outer radius of the confinement ring, an upper surface of the lower horizontal portion providing an angle that descends toward the lower inner radius, the lower horizontal portion having an extension that extends to the lower inner radius; a vertical portion disposed between the outer and inner radii of the confinement rings, the vertical portion connecting the upper horizontal portion to the lower horizontal portion of the confinement rings; A confinement ring comprising:

2. 10. The confinement ring of claim 1, a bottom surface of the lower horizontal portion is flat such that a first thickness of the lower horizontal portion near the inner radius is greater than a second thickness of the lower horizontal portion at the lower inner radius.

3. 3. The confinement ring of claim 2, The first thickness is about 10% to about 40% greater than the second thickness.

4. 10. The confinement ring of claim 1, The angle defines a slope along the top surface of the lower horizontal portion, the slope being between about 0.20° and about 1° as measured from a horizontal x-axis.

5. 10. The confinement ring of claim 1, a bottom surface of the lower horizontal portion presents a second angle decreasing toward the lower inner radius, the second angle defining a second slope along the bottom surface of the lower horizontal portion, the second angle of the second slope along the bottom surface being equal to the angle of the slope along the top surface of the lower horizontal portion, and a first thickness of the lower horizontal portion defined near the inner radius being equal to a second thickness of the lower horizontal portion defined at the lower inner radius.

6. 10. The confinement ring of claim 1, a first height defined between a bottom surface of the upper horizontal portion and the top surface of the lower horizontal portion near the inner radius is less than a second height defined between the bottom surface of the upper horizontal portion and the top surface of the lower horizontal portion at the lower inner radius of the confinement ring.

7. 10. The confinement ring of claim 1, The confinement ring, wherein the lower horizontal section, the vertical section, and the upper horizontal section are integrally connected to define a C-shaped structure.

8. 10. The confinement ring of claim 1, the lower horizontal portion further includes a plurality of slots, each slot extending radially along the lower horizontal portion from an inner diameter to an outer diameter, an inner slot radius of each slot at the inner diameter equal to an outer slot radius of each slot at the outer diameter.

9. 9. The confinement ring of claim 8, a confinement ring, wherein the inner diameter of the slot is greater than an inner ring diameter of the confinement ring defined by the lower inner radius, and the outer diameter of the slot is less than an outer ring diameter of the confinement ring defined by the outer radius.

10. 10. The confinement ring of claim 1, the lower horizontal portion further includes a plurality of slots, each slot extending radially along the lower horizontal portion from an inner diameter to an outer diameter, an inner slot radius of each slot at the inner diameter being smaller than an outer slot radius of each slot at the outer diameter.

11. 11. The confinement ring of claim 10, a difference between the inner slot radius and the outer slot radius of each slot defines a slot taper, each slot tapering from the outer diameter to the inner diameter, the inner slot radius and the outer slot radius affecting the slot taper being defined to be the reciprocal of the wear rate at the corresponding inner and outer diameters of the slot; A confinement ring, wherein the ratio of the inner slot radius to the outer slot radius is about 1:1.1 to 1:1.

5.

12. 10. The confinement ring of claim 1, The upper inner radius of the confinement ring is greater than the lower inner radius.

13. 10. The confinement ring of claim 1, The extension extends vertically downward at the lower inner radius of the confinement ring.

14. 10. The confinement ring of claim 1, the extension portion includes an angled top portion and a vertical bottom portion, the angled top portion providing a third angle that descends at a downwardly sloping point defined on the top surface at the lower inner radius of the lower horizontal portion, and the vertical bottom portion defined extending downwardly from a bottom portion of the angled top portion.

15. 10. The confinement ring of claim 1, a confinement ring, wherein the upper surface of the upper horizontal portion includes a plurality of holes, each of the plurality of holes configured to receive a portion of a fastening means defined on a bottom surface of the upper electrode to couple the confinement ring to the upper electrode of the plasma processing chamber.

16. 10. The confinement ring of claim 1, The confinement ring, wherein the extension of the lower horizontal section is configured to rest on a radio frequency gasket defined on an upper surface of a lower electrode of the plasma processing chamber.

17. 1. A confinement ring for use in a plasma processing chamber, comprising: an upper horizontal portion extending between an upper inner radius and an upper outer radius of the confinement ring; a lower horizontal portion extending between a lower inner radius and the outer radius of the confinement ring, wherein a top surface of the lower horizontal portion presents a first angle decreasing toward the lower inner radius to define a first slope along the top surface, and a bottom surface of the lower horizontal portion presents a second angle decreasing toward the lower inner radius to define a second slope along the bottom surface, the lower horizontal portion having an extension extending downwardly along the lower inner radius, the extension extending below the bottom surface of the lower horizontal portion; a vertical portion disposed between the outer and inner radii of the confinement rings, the vertical portion connecting the upper horizontal portion to the lower horizontal portion of the confinement rings; A confinement ring comprising:

18. 18. The confinement ring of claim 17, A confinement ring, wherein a first angle of the first slope is equal to the second angle of the second slope.

19. 18. The confinement ring of claim 17, a first thickness of the lower horizontal portion near the inner radius equal to a second thickness of the lower horizontal portion at the lower inner radius; a first height defined between the bottom surface of the upper horizontal portion and the top surface of the lower horizontal portion near the inner radius is less than a second height defined between the bottom surface of the upper horizontal portion and the top surface of the lower horizontal portion at the lower inner radius.

20. 18. The confinement ring of claim 17, the lower horizontal portion further includes a plurality of slots, each slot extending radially along the lower horizontal portion from an inner diameter to an outer diameter, an inner slot radius of each slot at the inner diameter equal to an outer slot radius of each slot at the outer diameter; a confinement ring, wherein the inner diameter of each slot is greater than an inner ring diameter of the confinement ring defined by the lower inner radius, and the outer diameter of each slot is less than an outer ring diameter of the confinement ring defined by the outer radius.

21. 18. The confinement ring of claim 17, the lower horizontal portion further includes a plurality of slots, each slot extending radially along the lower horizontal portion from an inner diameter to an outer diameter, an inner slot radius of each slot at the inner diameter being smaller than an outer slot radius of each slot at the outer diameter.

22. 1. A plasma processing chamber for containing a plasma, comprising: a lower electrode for supporting a substrate; and an upper electrode disposed above the lower electrode, a confinement ring disposed between the lower electrode and the upper electrode, an upper horizontal portion extending between an upper inner radius and an upper outer radius of the confinement ring; a lower horizontal portion extending between a lower inner radius and the outer radius of the confinement ring, an upper surface of the lower horizontal portion presenting an angle that descends toward the lower inner radius, the angle defining a slope along the upper surface, the lower horizontal portion having an extension that extends downwardly along the lower inner radius; a vertical portion disposed between the outer and inner radii of the confinement rings, the vertical portion connecting the upper horizontal portion to the lower horizontal portion of the confinement rings; 1. A plasma processing chamber comprising a confinement ring comprising:

23. 23. The plasma processing chamber of claim 22, a bottom surface of the lower horizontal section presenting a second angle decreasing toward the lower inner radius, the second angle defining a second slope along the bottom surface, the second angle of the second slope along the bottom surface being equal to the angle of the slope along the top surface of the lower horizontal section.

24. 23. The plasma processing chamber of claim 22, the lower horizontal portion further includes a plurality of slots disposed along the lower horizontal portion, each slot extending radially along the lower horizontal portion from an inner diameter to an outer diameter, an inner slot radius of each slot at the inner diameter being smaller than an outer slot radius of each slot at the outer diameter; A plasma processing chamber, wherein the inner diameter is greater than an inner ring diameter of the confinement ring defined by the lower inner radius, and the outer diameter is less than an outer ring diameter of the confinement ring defined by the outer radius.

25. 23. The plasma processing chamber of claim 22, The plasma processing chamber, wherein the upper inner radius is greater than the lower inner radius of the confinement ring.

26. 23. The plasma processing chamber of claim 22, the confinement ring defined by the lower horizontal section, the upper horizontal section, and the vertical section defines a continuous C-shaped structure for confining plasma generated in the plasma processing chamber to a plasma region, and the confinement ring is fabricated from one of silicon, polysilicon, silicon carbide, boron carbide, ceramic, and aluminum.

27. 23. The plasma processing chamber of claim 22, The plasma processing chamber, wherein the extension is integral with the lower horizontal portion, the vertical portion, and the upper horizontal portion of the confinement ring and is configured to extend vertically below a bottom surface of the lower horizontal portion.

28. 23. The plasma processing chamber of claim 22, The plasma processing chamber, wherein the upper electrode is electrically grounded and the lower electrode is connected to a radio frequency power source through a corresponding matching network.

Images