Polishing head with localized inner ring downforce control - Patents.com

Abstract

An exemplary carrier head for a chemical mechanical polishing apparatus may include a carrier body. The carrier head may include a substrate mounting surface coupled to the carrier body. The carrier head may include an inner ring sized and shaped to circumferentially surround a periphery of a substrate positioned relative to the substrate mounting surface. The inner ring may be characterized by a first surface facing the carrier body and a second surface opposite the first surface. The carrier head may include at least one downforce control actuator disposed above the first surface of the inner ring at discrete locations around the circumference of the inner ring.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. patent application Ser. No. 17 / 735,674, entitled "POLISHING HEAD WITH LOCAL INNER RING DOWNFORCE CONTROL," filed May 3, 2022, which is incorporated by reference in its entirety into this specification.

[0002]

[0002] The present technology relates to semiconductor systems, processes, and apparatus. In particular, the present technology relates to polishing a film deposited on a substrate. [Background technology]

[0003]

[0003] Integrated circuits are typically formed on a substrate by the successive deposition of conductive, semiconductive, and / or insulating layers on a silicon wafer. In various manufacturing processes, planarization of layers on the substrate occurs between processing steps. For example, in certain applications, such as polishing a metal layer to form vias, plugs, and lines in trenches in a patterned layer, the upper layer is planarized until the top surface of the patterned layer is exposed. In other applications, such as when a dielectric layer is planarized for photolithography, the upper layer is polished until a desired thickness remains above the lower layer.

[0004]

[0004] Chemical mechanical polishing (CMP) is one recognized method of planarization. This method of planarization typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is typically positioned against a rotating polishing pad. The carrier head applies a controllable load to the substrate, forcing it against the polishing pad. An abrasive slurry is typically supplied to the surface of the polishing pad for polishing.

[0005]

[0005] One problem in CMP is uniformly polishing the entire surface of a substrate. Due to the design of CMP systems, regions of the polishing pad near the periphery of the polishing pad often sag, which can lead to non-uniform polishing. Additionally, the lateral forces on the substrate may be different at the leading and / or trailing edges of the substrate. This can result in non-uniform film thickness across one or more edge regions of the substrate. This film non-uniformity can cause lithography problems and reduce die yield from a given substrate.

[0006]

[0006] Therefore, there is a need for improved systems and methods that can be used to polish a substrate to produce a uniform film across the entire surface area of ​​the substrate. These and other needs are addressed by the present technology. Summary of the Invention

[0007]

[0007] An exemplary carrier head for a chemical mechanical polishing apparatus may include a carrier body. The carrier head may include a substrate mounting surface coupled to the carrier body. The carrier head may include an inner ring sized and shaped to circumferentially surround a periphery of a substrate disposed relative to the substrate mounting surface. The inner ring may be characterized by a first surface facing the carrier body and a second surface opposite the first surface. The carrier head may also include an outer ring disposed radially outward of the inner ring. The carrier head may include at least one downforce control actuator disposed above the first surface of the inner ring at discrete locations around the circumference of the inner ring.

[0008]

[0008] In some embodiments, a magnitude of downforce applied by the at least one downforce control actuator to the discrete locations of the inner ring may be variable. The at least one downforce control actuator may include a plurality of downforce control actuators. Each of the plurality of downforce control actuators may be disposed at a different discrete location on the circumference of the inner ring. The at least one downforce control actuator may be disposed proximate to a trailing edge of the substrate. A magnitude of downforce applied by the at least one downforce control actuator to the discrete locations of the inner ring may be variable during a single polishing process. The at least one downforce control actuator may include a plunger contacting a first surface of the inner ring. The downforce applied by the plunger may be driven by an air cylinder. The substrate mounting surface may include a flexible membrane. The outer ring may have an inner surface disposed relative to an outer surface of the inner ring.

[0009]

[0009] Some embodiments of the present technology may include a carrier head for a chemical mechanical polishing apparatus. The carrier head may include a carrier body. The carrier head may include a substrate mounting surface coupled to the carrier body. The carrier head may include an inner ring sized and shaped to circumferentially surround a periphery of a substrate disposed relative to the substrate mounting surface. The inner ring may be characterized by a first surface facing the carrier body and a second surface opposite the first surface. The carrier head may also include an outer ring disposed radially outward of the inner ring. The carrier head may include a plurality of downforce control actuators disposed above the first surface of the inner ring. Each of the plurality of downforce control actuators may be disposed at a discrete location on the circumference of the inner ring.

[0010] In some embodiments, the multiple downforce control actuators may be regularly spaced around the circumference of the inner ring. A magnitude of downforce applied to the first surface of the inner ring may be different for at least one of the multiple downforce control actuators. At least some of the multiple downforce control actuators may be inactive during a given polishing process. A magnitude of downforce applied by each of the multiple downforce control actuators may be between about 0 lbs and 10 lbs. The multiple downforce control actuators may be arranged in an annular pattern concentric with the motor of the carrier head.

[0011]

[0011] Some embodiments of the present technique may include a method of polishing a substrate. The method may include flowing a polishing slurry from a slurry source to a polishing pad. The method may include polishing the substrate on the polishing pad. The method may include applying a localized downforce to one or more discrete locations of an inner ring that holds the substrate in a carrier head while polishing the substrate.

[0012]

[0012] In some embodiments, applying the local downforce may include pressurizing an air cylinder coupled to the plunger to press the plunger against an upper surface of the inner ring. The method may include adjusting a magnitude of the downforce applied to at least one of the one or more discrete locations while the substrate is being polished. During polishing, the magnitude of the local downforce may be constant throughout the duration of the polishing. The one or more discrete locations may be proximate to a trailing edge of the substrate. The method may include identifying a difference between a target polishing profile and an actual polishing profile. The method may include adjusting the local downforce for at least one of the one or more discrete locations of the inner ring based on the difference.

[0013]

[0013] Such techniques may provide numerous advantages over conventional systems and techniques. For example, the polishing heads described herein may help prevent over-polishing at edge regions of the substrate during the polishing process, particularly the trailing and / or leading edges. This may improve film thickness uniformity across the substrate surface and increase die yield. These and other embodiments, along with their many advantages and features, are described in more detail below and in the accompanying drawings.

[0014]

[0014] The nature and advantages of the techniques of the present disclosure may be further understood by reference to the remainder of this specification and the following drawings. [Brief description of the drawings]

[0015] [Figure 1]

[0015] A schematic cross-sectional view of an exemplary polishing system according to some embodiments of the present technique is shown. [Diagram 2]

[0016] 1 shows a schematic partial cross-sectional view of an exemplary carrier head, in accordance with some embodiments of the present technique; [Figure 2A]

[0017] 3 shows a schematic partial cross-sectional view of an inner ring of the carrier head of FIG. 2 in accordance with some embodiments of the present technology. [Diagram 3]

[0018] 1 shows a schematic partial cross-sectional view of an exemplary carrier head, in accordance with some embodiments of the present technique; [Figure 3A]

[0019] FIG. 4 is a schematic top view of the carrier head of FIG. 3. [Figure 4]

[0020] 1 is a flowchart of an exemplary method for polishing a substrate, in accordance with some embodiments of the present technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016]

[0021] Some of the drawings are included as schematic diagrams. It should be understood that the drawings are for illustrative purposes and should not be considered to scale unless expressly stated to be to scale. Furthermore, as schematic diagrams, the drawings are provided to aid in understanding and may not include all aspects or information compared to a realistic depiction and may include material that is emphasized for illustrative purposes.

[0017]

[0022] In the accompanying drawings, similar components and / or features may have the same reference numbers. Furthermore, various components of the same type may be distinguished according to the reference numbers, with a letter distinguishing between the similar components. If only a first reference number is used in this specification, the description is applicable to any of the similar components having the same first reference number, regardless of the letter.

[0018]

[0023] Conventional chemical mechanical polishing (CMP) processes often have difficulty polishing the surface of a substrate uniformly. In conventional CMP polishing, a substrate is placed face down on a polishing pad, and a carrier holds the substrate against the rotating pad. As the substrate is pressed across the polishing pad, the polishing pad often flexes near the edge of the substrate. Due to the hardness of the substrate, the flexing and subsequent rebound of the polishing pad can lead to non-uniform force concentrations near the edge region of the substrate. For example, pad rebound can result in higher material removal rates, which often occur at the trailing edge of the substrate. Often, depending on the type of polishing process being performed, polishing can be non-uniform near the trailing and / or leading edges of the substrate. These issues can lead to film non-uniformity issues, which can result in reduced die yields.

[0019]

[0024] The present technology overcomes these problems in conventional polishing systems by using a localized downforce control actuator to apply a downforce to the inner retaining ring of the carrier head. The downforce is used to control the deflection and / or rebound of the polishing pad, helping to ensure that non-uniform / over-polishing that may occur at one or more locations of the substrate is reduced. For example, downforce can be applied to one or more locations of the inner ring that correspond to areas of the substrate that experience more pad rebound to reduce the rebound and subsequently reduce the polishing / removal rate near the areas where the rebound has been reduced. In a particular embodiment, downforce can be applied to regions of the inner ring to combat removal rate issues caused by pad deflection and rebound near the trailing and / or leading edges of the inner ring. This can allow downforce control at one or more discrete locations to be used as a localized tuning knob for the edge of the substrate. These techniques can be used in conjunction with conventional CMP systems to produce substrates with improved film thickness uniformity.

[0020]

[0025] The remaining disclosure will be thorough and specific to a particular film polishing process utilizing the disclosed technology, but it will be readily understood that the systems and methods are equally applicable to a variety of other semiconductor processing steps and systems. Thus, the present technology should not be considered limited to use with the described polishing system or process alone. Before describing the systems and methods or steps of an exemplary process sequence according to some embodiments of the present technology, the present disclosure will describe one possible system that can be used with the present technology. It should be understood that the present technology is not limited to the described apparatus, and the described process may be performed in any number of processing chambers and systems with any number of modifications, some of which will be described below.

[0021]

[0026] FIG. 1 shows a schematic cross-sectional view of an exemplary polishing system 100 according to some embodiments of the present technique. The polishing system 100 includes a platen assembly 102 including a lower platen 104 and an upper platen 106. The lower platen 104 may define an interior space or cavity through which connections may be made. As well as, an endpoint detector or other sensor or device, such as an eddy current sensor, an optical sensor, or other component for monitoring the polishing process or components may be included within the interior space or cavity. For example, as described further below, fluid couplings may be formed with lines extending through the lower platen 104, which may access the upper platen 106 through the backside of the upper platen. The platen assembly 102 may include a polishing pad 110 mounted on a first surface of the upper platen. A substrate carrier 108 (or carrier head) may be disposed above and facing the polishing pad 110. The platen assembly 102 may be rotatable about axis A, and the substrate carrier 108 may be rotatable about axis B. The substrate carrier may also be configured to sweep back and forth along the platen assembly from the inner diameter to the outer diameter, in part to reduce uneven wear of the surface of the polishing pad 110. The polishing system 100 may also include a fluid delivery arm 118 disposed above the polishing pad 110, which may be used to deliver a polishing fluid (such as a polishing slurry) onto the polishing pad 110. Additionally, a pad conditioning assembly 120 may be disposed above and facing the polishing pad 110.

[0022]

[0027] In some embodiments of performing a chemical mechanical polishing process, a rotating and / or sweeping substrate carrier 108 can exert a down force on the substrate 112. The substrate 112, shown in phantom lines, can be disposed within the substrate carrier and can be coupled to the substrate carrier. The exerted down force can press the material surface of the substrate 112 down against the polishing pad 110 as the polishing pad 110 rotates about the central axis of the platen assembly. The interaction of the substrate 112 with the polishing pad 110 can occur in the presence of one or more polishing fluids delivered by a fluid delivery arm 118. A typical polishing fluid can include a slurry formed of an aqueous solution in which abrasive particles can be suspended. Often, the polishing fluid contains a pH adjuster and other chemically active components, such as an oxidizer, that can enable chemical mechanical polishing of the material surface of the substrate 112.

[0023]

[0028] The pad conditioning assembly 120 may be operable to apply a fixed polishing conditioning disk 122 to the surface of the polishing pad 110, which may be rotated as described above. The conditioning disk may be operated against the pad before, after, or during polishing of the substrate 112. Conditioning the polishing pad 110 with the conditioning disk 122 may maintain the polishing pad 110 in a desired condition by abrading, activating, and removing polishing by-products and other debris from the polishing surface of the polishing pad 110. The upper platen 106 may be disposed on a mounting surface of the lower platen 104 and may be coupled to the lower platen 104 using a number of fasteners 138 that extend through an annular flange-shaped portion of the lower platen 104.

[0024]

[0029] The polishing platen assembly 102, and thus the upper platen 106, may be appropriately sized for any desired polishing system and may be sized for any diameter substrate, including 200 mm, 300 mm, 450 mm, or more. For example, a polishing platen assembly configured to polish a 300 mm diameter substrate may be characterized by a diameter greater than about 300 mm, such as between about 500 mm and about 1000 mm, or greater than about 500 mm. The platens may be adjusted in diameter to accommodate substrates characterized by larger or smaller diameters, or for polishing platens 106 sized for simultaneous polishing of multiple substrates. The upper platen 106 may be characterized by a thickness between about 20 mm and about 150 mm, and may be characterized by a thickness of about 100 mm or less, such as about 80 mm or less, about 60 mm or less, about 40 mm or less, or less. In some embodiments, the ratio of diameter to thickness of the polishing platen 106 may be about 3:1 or more, about 5:1 or more, about 10:1 or more, about 15:1 or more, about 20:1 or more, about 25:1 or more, about 30:1 or more, about 40:1 or more, or about 50:1 or more, or more.

[0025]

[0030] The upper platen and / or the lower platen may be formed of a suitably rigid, lightweight and polishing fluid resistant material, such as aluminum, aluminum alloy, or stainless steel, although any number of materials may be used. The polishing pad 110 may be formed of any number of materials, such as polymeric materials, such as polyurethane, polycarbonate, fluoropolymer, polytetrafluoroethylene, polyphenylene sulfide, or combinations of these or other materials. The additional materials may be or include open or closed cell foamed polymers, elastomers, felts, impregnated felts, plastics, or any other materials that may be compatible with the process chemicals. The polishing system 100 is included to provide appropriate references to the components described below that may be incorporated into the system 100, but it will be understood that the description of the polishing system 100 is not intended to limit the present technology in any manner, as embodiments of the present technology may be incorporated into any number of polishing systems that may benefit from the components and / or features as described further below.

[0026]

[0031] 2 shows a schematic cross-sectional side view of an exemplary carrier head 200 according to some embodiments of the present technique. The carrier head 200 may show a partial view of the described components that may be incorporated into a polishing system similar to the polishing system 100. The carrier head 200 may be used as a substrate carrier 108 in some embodiments. The carrier head 200 may include a housing 202, a base assembly 204 (the housing 202 and the base assembly 204 may be referred to as a carrier body), a gimbal mechanism 206 (which may be considered part of the base assembly 204), a load chamber 208, an inner ring assembly including an inner ring 240 and a first flexible membrane 270 shaped to provide an annular chamber 272, an outer ring 260, and a substrate backing assembly 210 that may include a second flexible membrane 250 that defines a plurality of pressurizable chambers.

[0027]

[0032] The housing 202 may have a generally circular shape and be connected to a drive shaft that rotates therewith during polishing. There may be a passage (not shown) extending through the housing 202 for gas pressure control of the carrier head 200. The base assembly 204 may be a vertically movable assembly disposed below the housing 202. The gimbal mechanism 206 may allow the base assembly 204 to gimbal relative to the housing 202 while preventing lateral movement of the base assembly 204 relative to the housing 202. A load chamber 208 may be disposed between the housing 202 and the base assembly 204 to apply a load (i.e., downward pressure or weight) to the base assembly 204. The vertical position of the base assembly 204 relative to the polishing pad (such as the polishing pad 110) may also be controlled by the load chamber 208. The substrate backing assembly 210 may include a flexible membrane 250 having a lower surface 252 that may provide a mounting surface for the substrate 280.

[0028]

[0033] The substrate 280 may be held by an inner ring assembly. The inner ring assembly may be clamped to the base assembly 204. The inner ring assembly may be constructed from an inner ring 240 shaped to provide an annular chamber 252 and a flexible membrane 270. The inner ring 240 may be configured to be positioned below and secured to the flexible membrane 270.

[0029]

[0034] As best shown in FIG. 2A, the inner ring 240 is an annular body having an inner surface 242, a first surface 244 facing the carrier body, a second surface 246 opposite the first surface 244 (facing and coming into contact with the polishing pad), and an outer surface 248. A lower region of the inner surface 242 adjacent the second surface 246 may be a generally vertical cylindrical surface and configured to circumferentially surround the edge of the substrate 280 to hold the substrate 280 during polishing. The lower region of the inner surface 242 may have an inner diameter slightly larger than the diameter of the substrate (approximately 1-2 mm larger than the diameter of the substrate) to accommodate the placement tolerance of the substrate loading system. The upper region of the inner surface 242 may be a generally vertical cylindrical surface and may be slightly recessed relative to the lower region. For example, the inner radial diameter of the upper region of the inner surface 242 may be larger than the inner radial diameter of the lower region of the inner surface 242. In some embodiments, a tapered region may connect the lower region to the upper region.

[0030]

[0035] The lower region of the outer surface 248 adjacent the second surface 246 may be a vertical cylindrical surface. The portion of the inner ring 240 between the lower region of the inner surface 242 and the lower region of the outer surface 248 may provide a lower annular ring having a width of, for example, 0.04 to 0.20 inches, for example, 0.05 to 0.15 inches. The upper region of the outer surface 248 adjacent the first surface 244 may be a vertical cylindrical surface. The lower region of the outer surface 248 may be recessed relative to the upper region. For example, the outer radial diameter of the upper region may be larger than the outer radial diameter of the lower region of the outer surface 248. The portion of the inner ring 240 between the upper region of the inner surface 242 and the upper region of the outer surface 248 may provide an upper annular ring that is wider than the lower annular ring. The outer radial diameter of the lower ring (i.e., the lower region of the outer surface 248) may be larger than the inner radial diameter of the upper ring (i.e., the upper region of the inner surface 242).

[0031]

[0036] The second surface 246 of the inner ring 240 may contact the polishing pad. At least the lower portion of the inner ring 240, including the second surface 246, may be formed of a material that is chemically inert in the CMP process, such as plastic (e.g., polyphenylene sulfide (PPS)). The lower portion should also be durable and have a low wear rate. In addition, the lower portion should be sufficiently compressible so that contact of the substrate edge against the inner ring does not result in the substrate being chipped or cracked. On the other hand, the lower portion should not be so elastic that downward pressure on the inner ring 240 would cause the lower portion to be pushed into the substrate-receiving recess. In some embodiments, the upper portion of the inner ring 240 may be formed of a harder material than the lower portion. For example, the lower portion may be plastic (e.g., PPS) and the upper portion may be metal (e.g., stainless steel, molybdenum, or aluminum) or ceramic (e.g., alumina).

[0032]

[0037] In some implementations, the inner ring 240 may include one or more slurry transport channels formed in the lower surface. The slurry transport channels may extend from the inner diameter to the outer diameter of the lower ring portion to allow slurry to pass from the exterior to the interior of the inner ring 240 during polishing. The slurry transport channels may be evenly spaced around the inner ring in some embodiments. Each slurry transport channel may be offset at an angle of, for example, 45 degrees relative to the radius passing through the channel. The channels may have a width of about 0.125 inches.

[0033]

[0038] In some implementations, the inner ring 240 may have one or more through holes extending through the body of the inner ring 240 from the inner surface 242 to the outer surface 248 to allow fluid (e.g., air or water) to pass from the interior to the exterior or from the exterior to the interior of the inner ring 240 during polishing. The through holes may extend through the upper ring. The through holes may be uniformly spaced around the inner ring 240 in some embodiments.

[0034]

[0039] In some embodiments, the upper portion of the inner ring 240 may be wider at the bottom than at the top. For example, the inner surface 242 may have a tapered region that slopes inwardly (i.e., has a decreasing diameter) from top to bottom below the vertical region. The inner surface of the lower portion may be generally vertical. When the lower portion of the inner ring 240 wears during substrate polishing, the narrower upper inner surface of the inner ring 240 may prevent wear against the adjacent flexible membrane 270 that provides the substrate mounting surface. Additionally, in some embodiments, the entire outer surface 248 of the inner ring 240 may be coated with a non-stick coating (e.g., parylene).

[0035]

[0040] The flexible membrane 250 may be configured to be clamped to the base assembly 204 above and positioned against the inner ring 240 below. Positioning the flexible membrane between the inner ring 240 and the carrier head 200 can reduce or eliminate the effect of carrier distortion on the inner ring 240 that occurs when the ring 240 is directly secured to the carrier head 200. This elimination of carrier distortion reduces uneven wear of the inner ring 240, reduces process variations at the substrate edge, allows lower polishing pressures to be used, and increases ring life. The flexible membrane 250 may be formed of a resilient material, allowing the membrane to flex under pressure. The resilient material may include silicone and other exemplary materials.

[0036]

[0041] While the inner ring 240 is configured to hold the substrate 280 and provide active edge process control, the outer ring 260 may provide a positioning or reference for the carrier head 200 relative to the surface of the polishing pad. In addition, the outer ring 260 may contact the inner ring 240 and provide a lateral reference for the inner ring 240. The outer ring 260 circumferentially surrounds the inner ring 240. Similar to the inner ring 240, the lower surface of the outer ring 260 may contact the polishing pad. The lower surface of the outer ring 260 may be a smooth, abrasive surface and may be selected to not abrade the polishing pad. The upper surface of the outer ring 260 may be fixed to the base 204. For example, the outer ring 260 may not be able to move vertically relative to the base 204. In some embodiments, the upper portion of the outer ring 260 may be formed of a harder material than the lower portion of the outer ring 260. For example, the lower portion may be a plastic, such as polyetheretherketone (PEEK), carbon-filled PEEK, Teflon-filled PEEK, polyamideimide (PAI), or a composite material, while the upper portion may be a metal, such as stainless steel, molybdenum, aluminum, or a ceramic, such as alumina. A portion of the outer ring 260, including the lower surface, may be formed of a harder material than a portion of the inner ring 240, including the second surface 246. As a result, the outer ring 260 may wear at a lower rate than the inner ring 240. For example, the lower portion of the outer ring 260 may be a plastic that is harder than the plastic of the inner ring 240.

[0037]

[0042] FIG. 3 shows a schematic cross-sectional side view of an exemplary carrier head 300 according to some embodiments of the present technique. The carrier head 300 can be used to perform a substrate polishing process. FIG. 3 can show a partial view of the described components, which can be incorporated into a chemical mechanical polishing system, such as the polishing system 100 described herein. The carrier head 300 can be used as the carrier head 108 and / or the carrier head 200 in some embodiments and can be understood to include any of the features described in connection with the carrier heads 108 and 200. The carrier head 300 can include a carrier body 302. The carrier body 302 can include a housing and base assembly in some embodiments, as described in connection with FIG. 2. The carrier head 300 can include a substrate mounting surface 304, such as a flexible membrane. The substrate mounting surface 304 can be coupled to a bottom end of the carrier body 302. The substrate mounting surface 304 can be used to engage and apply downward pressure to the backside of a substrate during a polishing process.

[0038]

[0043] The carrier head 300 may include an inner ring 306. The inner ring 306 may be similar to the inner ring 240 described above. For example, the inner ring 306 may be coupled to the carrier body 302 and engage a polishing pad. The inner ring 306 may be characterized by a first surface 308 (e.g., an upper surface) that faces the carrier body 302 and a second surface 310 (e.g., a lower surface) opposite the first surface 308. The annular body 306 may be sized and shaped to circumferentially surround a periphery of a substrate disposed against the substrate mounting surface 304. For example, the bottom end of the inner ring 306 (proximate the second surface 310) may have an inner diameter that is larger than the diameter of the substrate to be polished by a small amount (e.g., about 5 mm or less, about 4 mm or less, about 3 mm or less, about 2 mm or less, about 1 mm or less, about 0.5 mm or less). The inner ring 306 may thereby act as a retaining ring to prevent the substrate from falling out of engagement with the substrate mounting surface 304 during the polishing process.

[0039]

[0044] The second surface 310 may contact a polishing pad (and polishing slurry) during polishing of a substrate. The second surface 310 may be formed of a material that is chemically inert in a CMP process, such as a plastic (e.g., polyphenylene sulfide (PPS)). The inner ring 306 may be substantially immobile in a vertical direction (e.g., a direction extending through the first surface 308 and the second surface 310) and / or a horizontal direction, or may have some degree of flexibility (e.g., compressibility) in the vertical and / or horizontal directions.

[0040]

[0045] The carrier head 300 may include an outer ring 312 that may provide a location or reference for the carrier head 200 relative to the surface of the polishing pad. In addition, the outer ring 312 may contact and circumferentially surround the inner ring 306. An upper surface of the outer ring 312 may be bonded to the carrier body 302. A lower surface of the outer ring 312 may come into contact with the polishing pad. The lower surface of the outer ring 312 may be a smooth, abrasive surface and may be selected to not abrade the polishing pad. The outer ring 312 may help inhibit movement and / or deformation of the lower end of the inner ring 306 during the polishing process.

[0041]

[0046] The carrier head 300 may include one or more downforce control actuators 314. Each downforce control actuator 314 may be positioned to align with the first surface 308 of the inner ring 306 at a discrete location around the circumference of the inner ring 306. For example, each downforce control actuator 314 may be positioned above the first surface 308 of the inner ring 306. The downforce control actuators 314 may thereby selectively apply a downforce to the first surface 308 at the discrete locations. The downforce may press the second surface 310 of the inner ring 306 against the polishing pad near the periphery of the substrate. This changes the amount of pad deflection and / or rebound in an area proximate each downforce control actuator 314. For example, in areas of the substrate where pad rebound may be greater (such as the trailing edge and / or leading edge), a downforce may be applied to the inner ring 306 to reduce the amount of pad rebound. This can help reduce and / or eliminate areas of high or low removal rates, contributing to a more uniform film thickness profile across the surface of the substrate.

[0042]

[0047] The operating state (e.g., on / active or off / inactive) of each downforce control actuator 314 and / or the magnitude of the downforce applied to the inner ring 306 at each downforce control actuator 314 may be controlled to vary the amount of deflection and / or rebound of the polishing pad to adjust and / or otherwise control the polishing rate across the substrate, particularly near the edge region of the substrate (such as the leading edge and / or trailing edge). In some embodiments, each downforce control actuator 314 may provide a downforce between about 0 kg and 5 kg. For example, the applied downforce may be about 5 kg or less, about 4.5 kg or less, about 4 kg or less, about 3.5 kg or less, about 3 kg or less, about 2.5 kg or less, about 2 kg or less, about 1.5 kg or less, about 1 kg or less, about 0.5 kg or less, or less. The magnitude of the downforce applied by each of the downforce control actuators 314 may be constant and / or variable in some embodiments. For example, the downforce may be adjusted to have a predetermined magnitude for a given polishing recipe. In some embodiments, the magnitude of the downforce can be adjusted and / or switched on and / or off during the polishing process. For example, the magnitude of the downforce can be increased and / or decreased midway through the polishing process. Such adaptive downforce control can be used to improve polishing rate / film uniformity and / or otherwise help achieve a desired polishing rate / film thickness profile.

[0043]

[0048] In some embodiments including multiple downforce control actuators 314, each downforce control actuator 314 may apply the same magnitude of downforce, while in other embodiments, at least one downforce control actuator 314 applies a downforce of a different magnitude (including zero) than at least one other downforce control actuator 314. In some embodiments, each downforce control actuator 314 may provide a different magnitude of downforce. Each of the downforce control actuators 314 may be independently controllable, such that the operating state (i.e., on or off) and / or magnitude of downforce applied by a given downforce control actuator 314 may be controlled independently of each of the other downforce control actuators 314. For example, all or some of the downforce control actuators 314 may be active or inactive during a given polishing process to produce a desired film thickness profile.

[0044]

[0049] Each downforce control actuator 314 may take the form of a linear actuator. The linear actuator is configured to selectively apply a constant and / or variable magnitude of downforce at discrete locations. The linear actuator may take many forms, such as, but not limited to, mechanical and / or electromechanical actuators (e.g., lead screws, jack screws, ball screws, roller screws, cam actuators, bellows with guide systems, flexure / lever systems, etc.), hydraulic actuators, and / or pneumatic actuators. In one particular embodiment, the downforce control actuators 314 may each include a plunger 316 disposed within an air cylinder 318. The air cylinder 318 may be fluidly coupled to an air pressure source 320. The air pressure source 320 may selectively control the flow of air to the air cylinder 318 to control the pressure within the air cylinder 318. The pressure in the air cylinder 318 causes the plunger 316 to press against the first surface 308 of the inner ring 306 and control the downforce applied to the polishing pad from the second surface 310 of the inner ring 306. Thus, a higher pressure in the air cylinder 318 results in a larger downforce applied by the plunger 316. In some embodiments, the plunger 316 (or other force applicator of the downforce control actuator 314) may directly contact the first surface 308 of the inner ring 306, while in other embodiments, one or more intervening components may be disposed between the force applicator to transfer the downforce from the downforce control actuator 314 to the inner ring 306.

[0045]

[0050] Each downforce control actuator 314 may apply any downforce to the inner ring 308 over a contact area. The contact area is determined by the contact surface of the force applicator of the downforce control actuator 314 and / or the contact surface of the intervening components that contact and transmit downforce to the inner ring 308. In one particular embodiment, the contact area may be defined by the size of the arc of the inner ring 308 that is actually contacted by the downforce transmitting component. The contact area for each downforce control actuator 314 may be about 10 degrees or less, about 9 degrees or less, about 8 degrees or less, about 7 degrees or less, about 6 degrees or less, about 5 degrees or less, about 4 degrees or less, about 3 degrees or less, about 2 degrees or less, about 1 degree or less, about 0.5 degrees or less, or less of the circumference of the inner ring 308. In some embodiments, the downforce applied by a given downforce control actuator 314 may be substantially concentrated at a portion of the inner ring 306 that is disposed below and contacted by the downforce control actuator 314. In other embodiments, the downforce applied by a given downforce control actuator 314 may be distributed circumferentially along the inner ring 306 to affect a larger arc of the inner ring 306. For example, the downforce applied by a given downforce control actuator 314 may be distributed circumferentially along at least about 0.5 degrees, at least about 1 degree, at least about 2 degrees, at least about 5 degrees, at least about 10 degrees, at least about 15 degrees, at least about 20 degrees, at least about 30 degrees, or more of the inner ring 306 beyond the contact area (in one or both directions). The spread of the downforce may be controlled by the vertical elasticity and / or compressibility of the inner ring 306 in some embodiments. For example, a stiffer inner ring 306 can spread the downforce over a larger circumferential area than a more elastic / compressible inner ring 306.In some embodiments, a more elastic / compressible inner ring 306 can be utilized to provide a more precisely controllable amount of downforce control to combat any polishing rate non-uniformity issues associated with pad deflection and / or pad rebound.

[0046]

[0051] In some embodiments, a single downforce control actuator 314 may be included in the carrier head 300. For example, only a single region of the substrate (such as, but not limited to, the trailing edge or leading edge) may be determined to be experiencing edge uniformity problems during polishing. The single downforce control actuator 314 may be located at or proximate to (e.g., within about 20 degrees, within about 15 degrees, within about 10 degrees, within about 5 degrees, within about 3 degrees, within about 1 degree, or below) the region experiencing edge uniformity problems. In other embodiments, the carrier head 300 may include multiple downforce control actuators 314. For example, carrier head 300 may include at least about two downforce control actuators 314, at least about three downforce control actuators 314, at least about four downforce control actuators 314, at least about five downforce control actuators 314, at least about six downforce control actuators 314, at least about seven downforce control actuators 314, at least about eight downforce control actuators 314, at least about nine downforce control actuators 314, at least about ten downforce control actuators 314, at least about eleven downforce control actuators 314, at least about twelve downforce control actuators 314, or more.

[0047]

[0052] In embodiments using multiple downforce control actuators 314, each downforce control actuator 314 may be located at a different discrete location around the circumference of the inner ring 306. The downforce control actuators 314 may be regularly and / or irregularly spaced around the circumference of the inner ring 306. For example, as shown in the schematic top view of FIG. 3A, in some embodiments, the downforce control actuators 314 may be arranged in an annular pattern concentric with the inner ring 306, the carrier head 300, and the motor driving the rotation of the carrier head 300. In other embodiments, the downforce control actuators 314 may be located only in one or more regions around the circumference of the inner ring 306. For example, the downforce control actuators 314 may be located in areas that are likely to have non-uniform polishing rates due to flexing / rebound of the polishing pad. For example, the downforce control actuators 314 may be located only at and / or adjacent to the trailing edge and / or leading edge regions of the substrate / inner ring 306. It will be appreciated that when multiple downforce control actuators 314 are included within the carrier head 300, any number (including zero) of downforce control actuators 314 may be active during a given polishing process. The operating conditions and / or magnitude of the downforce exerted by each downforce control actuator 314 may be customized for a given polishing process (and in some cases may be varied during the process) to produce a desired film thickness.

[0048]

[0053] 4 illustrates exemplary steps in a method 400 for polishing a substrate, according to some embodiments of the present technique. The method 400 may be performed using a carrier head, such as carrier head 108, 200, or 300 described herein. The method 400 may include steps prior to substrate polishing, in some embodiments. For example, prior to polishing, the substrate may undergo one or more deposition and / or etching steps, as well as planarization or other process steps. The method 400 may include some steps that may be performed automatically in a system to limit manual interaction and provide greater efficiency and accuracy than manual interaction. The method 400 may be performed as part of or in conjunction with a conventional CMP polishing process.

[0049]

[0054] The method 400 may include flowing a polishing slurry from a slurry source to a polishing pad in step 405. In step 410, a substrate may be polished on the polishing pad. For example, the substrate may be placed in a carrier head. The carrier head rotates and / or translates (or sweeps) the substrate around the surface of the polishing pad. The abrasive particles in the polishing slurry may thereby gradually remove material from the surface of the substrate in a desired pattern and / or to achieve a desired film thickness profile. In some embodiments, the polishing pad may rotate and / or translate in addition to or instead of the carrier head rotating and / or translating. The backside of the substrate may be placed against a substrate mounting surface, such as a flexible membrane, which may be used to apply pressure to the backside of the substrate during the polishing process. The substrate may be held in a desired position relative to the carrier head and flexible membrane using an inner ring disposed radially outward of the substrate. To counteract non-uniform polishing rates that may occur due to polishing pad deflection and / or rebound as the substrate and polishing pad surface move relative to one another, a localized downforce may be applied to one or more discrete locations of the inner ring (such as at or near the trailing and / or leading edges) in step 415. This downward force may be used to increase pad deflection and / or reduce pad rebound to produce a more uniform polishing rate across the surface of the substrate, particularly in edge regions such as at or near the trailing and / or leading edges of the substrate.

[0050]

[0055] Applying a localized downforce may be performed using one or more downforce control actuators, such as downforce control actuator 314. In one particular embodiment, downforce control actuator 314 may include a plunger driven by an air cylinder. The air cylinder may be pressurized, such as by supplying air or other fluid from a pneumatic source to the air cylinder. The air cylinder may push the plunger to apply a downward force (directly or indirectly) to a top surface of the inner ring. This downward force may push a portion of the inner ring proximate to the downforce control actuator 314 downwardly into the polishing pad to increase deflection and / or reduce rebound in a given area. The magnitude of the downforce may be constant in some embodiments, while in other embodiments the magnitude of the downforce may be changed or otherwise adjusted at one or more discrete locations while the substrate is being polished.

[0051]

[0056] In some embodiments, the method 400 may optionally include identifying a difference between the target polishing profile and the actual polishing profile. For example, polishing time, pattern (e.g., sweeping motion, rotation, etc.), and / or other factors may be selected to polish the substrate to a desired or target film thickness profile (which may be substantially uniform in some embodiments). However, due to factors such as pad deflection and pad rebound, there may be a non-uniform polishing rate at certain regions of the substrate, such as near the trailing edge and / or leading edge. Measurements of the polished substrate may be made to determine whether there is any difference between the actual film thickness profile and the target polishing profile that the polishing process is intended to achieve. Based on an analysis of such differences, the local downforce for at least one of the downforce control actuators may be adjusted. For example, if it is determined that there is excessive wear (e.g., film is too thin) at the trailing edge of the substrate, the magnitude of the local downforce that may be applied at or adjacent to the trailing edge using one or more downforce control actuators may be increased, thereby reducing pad rebound in that region and subsequently reducing the removal rate. This may help make the polishing rate more uniform across the surface of the substrate. In particular, the magnitude of the downforce for one or more discrete locations of the inner ring may be identified by experimentation. For example, multiple test substrates may be polished using different combinations of downforces applied to one or more discrete locations of the inner ring, but otherwise using the same process parameters for polishing the device substrates. The uniformity of the test substrates in the near-edge area (or other regions) may be measured, for example, using a stand-alone metrology unit. The pressure combination that provided the best polishing uniformity (or otherwise closest to the target film thickness profile) may be selected for subsequent polishing of the device substrates.

[0052]

[0057] In the foregoing description, for purposes of explanation, numerous details are presented in order to facilitate an understanding of various embodiments of the present technology. However, it will be apparent to one of ordinary skill in the art that certain embodiments may be practiced without some of these details, or with additional details.

[0053]

[0058] Although several embodiments have been disclosed, those skilled in the art will recognize that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Moreover, some well-known processes and elements have not been described to avoid unnecessarily obscuring the technology. Thus, the above description should not be construed as limiting the scope of the technology.

[0054]

[0059] Where a range of values ​​is provided, it is to be understood that each intervening value between the upper and lower limits of that range is specifically disclosed, to the smallest unit of the lower limit, unless the context clearly indicates otherwise. Any smaller ranges between any stated or unstated intervening value in a stated range, as well as any other stated or intervening value in that stated range, are also included. The upper and lower limits of these smaller ranges may be individually included or excluded from the range, and each range in which either, neither or both limits are included in the smaller ranges is also encompassed within the scope of the technology, subject to any specifically excluded limits in the stated range. Where a stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

[0055]

[0060] As used in this specification and claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to a "heater" includes a plurality of such heaters, a reference to a "protrusion" includes a reference to one or more protrusions and equivalents thereof known to those skilled in the art, and so forth.

[0056]

[0061] Additionally, the terms "comprises," "comprising," "containing," "containing," "including," and "including," when used in this specification and claims, are intended to specify the presence of stated features, integers, components, or steps, but do not exclude the presence or addition of one or more other features, integers, components, steps, operations, or groups.

Claims

1. Carrier body, a substrate mounting surface coupled to the carrier body; an inner ring sized and shaped to circumferentially surround a peripheral edge of a substrate positioned against the substrate mounting surface, the inner ring being characterized by a first surface facing the carrier body and a second surface opposite the first surface; an outer ring disposed radially outward of the inner ring; and at least one downforce control actuator disposed above the first surface of the inner ring at discrete locations around the circumference of the inner ring; A carrier head for a chemical mechanical polishing apparatus, wherein each of the at least one downforce control actuator exerts a downforce on the inner ring over a contact area of ​​about 10 degrees or less of a circumference of the inner ring.

2. 2 . The carrier head of claim 1 , wherein the magnitude of downforce exerted by the at least one downforce control actuator at the discrete locations on the inner ring is variable.

3. 2. The carrier head for a chemical mechanical polishing apparatus of claim 1 , wherein the at least one downforce control actuator comprises a plurality of downforce control actuators, each of the plurality of downforce control actuators disposed at a different discrete location on the circumference of the inner ring.

4. The carrier head for a chemical mechanical polishing apparatus of claim 1 , wherein the at least one downforce control actuator is positioned proximate to a trailing edge of the substrate.

5. 2 . The carrier head for a chemical mechanical polishing apparatus of claim 1 , wherein a magnitude of downforce exerted by the at least one downforce control actuator at the discrete locations on the inner ring is variable during a single polishing process.

6. the at least one downforce control actuator comprises a plunger contacting the first surface of the inner ring; 10. The carrier head for a chemical mechanical polishing apparatus of claim 1, wherein the down force exerted by the plunger is driven by an air cylinder.

7. The carrier head for a chemical mechanical polishing apparatus of claim 1 , wherein the substrate mounting surface comprises a flexible membrane.

8. 2 . The carrier head for a chemical mechanical polishing apparatus of claim 1 , wherein the outer ring has an inner surface disposed against an outer surface of the inner ring.

9. Carrier body, a substrate mounting surface coupled to the carrier body; an inner ring sized and shaped to circumferentially surround a peripheral edge of a substrate positioned against the substrate mounting surface, the inner ring being characterized by a first surface facing the carrier body and a second surface opposite the first surface; an outer ring disposed radially outward of the inner ring; and 1. A carrier head for a chemical mechanical polishing apparatus comprising: a plurality of downforce control actuators disposed above the first surface of the inner ring, each downforce control actuator being disposed at discrete locations around the circumference of the inner ring and applying a downforce to the inner ring over a contact area of ​​about 10 degrees or less around the circumference of the inner ring.

10. 10. The carrier head for a chemical mechanical polishing apparatus of claim 9, wherein the plurality of downforce control actuators are regularly spaced about the circumference of the inner ring.

11. 10. The carrier head of claim 9, wherein a magnitude of downforce applied to the first surface of the inner ring is different from at least one of the plurality of downforce control actuators.

12. 10. The carrier head for a chemical mechanical polishing apparatus of claim 9, wherein at least some of the plurality of downforce control actuators are inactive during a given polishing process.

13. 10. The carrier head of claim 9, wherein the magnitude of the downforce exerted by each of the plurality of downforce control actuators is between about 0 lbs and 10 lbs.

14. 10. The carrier head of claim 9, wherein the plurality of downforce control actuators are arranged in an annular pattern concentric with a motor of the carrier head.

15. flowing a polishing slurry from a slurry supply onto a polishing pad; polishing a substrate on the polishing pad; and applying a localized down force to one or more discrete locations of an inner ring that retains the substrate within a carrier head while polishing the substrate; A method of polishing a substrate, wherein the contact area at each of the one or more discrete locations is less than or equal to about 10 degrees of a circumference of the inner ring.

16. 16. The method of polishing a substrate of claim 15, wherein applying the localized down force comprises pressurizing an air cylinder coupled to the plunger to press the plunger against a top surface of the inner ring.

17. 16. The method of polishing a substrate of claim 15, further comprising adjusting a magnitude of a down force applied to at least one of the one or more discrete locations while the substrate is being polished.

18. 16. The method of polishing a substrate of claim 15, wherein the magnitude of the local down force is constant throughout the duration of the polishing.

19. The method of polishing a substrate of claim 15 , wherein the one or more discrete locations are proximate a trailing edge of the substrate.

20. Identifying a difference between the target polishing profile and the actual polishing profile; and 16. The method of polishing a substrate of claim 15, further comprising adjusting the local down force for at least one of the one or more discrete locations of the inner ring based on the difference.

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