Retaining ring having inner surface including feature

Abstract

To provide a retaining ring capable of improving more preferable uniformity of a thickness of a polished substrate.SOLUTION: Some implementations of a retaining ring have an inner surface having a first portion that is formed of multiple planar facets, and a second portion that adjoins the first portion along a boundary and includes a frustoconical surface that is sloped downwardly from outside in. Some implementations of the retaining ring have a crenellated or serpentine inner surface, and / or an inner surface with alternating region of different surface properties or different tilt angles.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure generally relates to chemical mechanical polishing of a substrate, and more particularly to a retaining ring used in chemical mechanical polishing.

Background Art

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconductive, or insulating layers on a silicon wafer. A manufacturing step includes depositing a fill layer on a non-planar surface and planarizing the fill layer until the non-planarity is exposed. For example, a conductive fill layer can be deposited on a patterned insulating layer to fill trenches or holes within the insulating layer. The fill layer is then polished until the raised pattern of the insulating layer is exposed. After planarization, the portions of the conductive layer remaining between the raised patterns of the insulating layer form vias, plugs, and lines that provide conductive paths between thin film circuits on the substrate. Additionally, planarization may be required to planarize a dielectric layer at the surface of the substrate for photolithography.

[0003] Chemical mechanical polishing (CMP) is one of the recognized planarization methods. In this polishing method, generally, it is necessary to attach the substrate to a carrier or a polishing head of a CMP apparatus. The exposed surface of the substrate is disposed against a rotating polishing disk pad or a belt pad. The polishing pad can be either a "standard" pad or a fixed abrasive polishing pad. The standard pad has a durable rough surface, while the fixed abrasive polishing pad has abrasive particles held in a containment medium. The carrier head applies a controllable load to the substrate and presses the substrate against the polishing pad. A polishing slurry containing at least one chemical reactant (and abrasive particles if a standard pad is used) is supplied to the surface of the polishing pad.

[0004] The substrate is typically held under the carrier head by a retaining ring. However, since the retaining ring contacts the polishing pad, it is prone to wear and is occasionally replaced. There are retaining rings that have a metal upper part and a plastic lower part that can wear, while other retaining rings are single plastic components. SUMMARY OF THE INVENTION

[0005] In one aspect, the retaining ring includes an annular body having an upper surface configured to be fixed to the carrier head, a bottom surface configured to contact the polishing surface, an outer surface extending from the upper surface around the outer upper periphery to the bottom surface around the outer bottom periphery, and an inner surface extending from the upper surface around the inner upper periphery to the bottom surface around the inner bottom periphery. The inner surface includes a first portion adjacent to the bottom surface and a second portion proximate to the first portion along a boundary line. The first portion includes seven or more facets. The periphery around the inner bottom is defined by the bottom edges of the facets. The second portion may include a frustoconical surface that slopes downwardly from outside in.

[0006] Embodiments may include one or more of the following features. The facets may be planar. Adjacent facets may be joined by straight side edges. The periphery around the inner bottom may be defined by the straight bottom edges of the planar facets. The boundary line includes a plurality of curved edges corresponding to the plurality of facets, and each curved edge with respect to a facet may have a lowest point at the horizontal center of the facet. The annular body may include an upper part and a lower part of a material different from the upper part. The lowest point of each curved edge may be aligned with the boundary line between the upper part and the lower part. The bottom surface may include channels extending from the outer surface to the inner surface. Each channel may include an end open to the inner surface of the body with straight side edges. The inner surface includes a first number of facets, the bottom surface has a second number of channels, and the first number may be an integer multiple of the second number. The integer may be 3, 4, or 5. The inner surface may have a total of 72 facets. The periphery around the inner bottom may be a regular polygon.

[0007] In another aspect, the retaining ring includes an annular body having an upper surface configured to be fixed to the carrier head, a bottom surface configured to contact the polishing surface, an outer surface extending from the upper surface around the outer upper periphery to the bottom surface around the outer bottom periphery, and an inner surface extending from the upper surface around the inner upper periphery to the bottom surface around the inner bottom periphery. The inner surface includes a plurality of inwardly extending protrusions each having a flat innermost surface.

[0008] In another aspect, the retaining ring includes an annular body having an upper surface configured to be fixed to the carrier head, a bottom surface configured to contact the polishing surface, an outer surface extending from the upper surface around the outer upper periphery to the bottom surface around the outer bottom periphery, and an inner surface extending from the upper surface around the inner upper periphery to the bottom surface around the inner bottom periphery. The innermost surface includes a plurality of inwardly extending protrusions that provide a serpentine path around the inner bottom periphery.

[0009] In another aspect, a method of forming a retaining ring includes joining an upper portion of the retaining ring having a frustoconical inner surface to a lower portion of the retaining ring having a cylindrical inner surface, and machining the inner surface of the lower portion and the inner surface of the upper portion to form a plurality of flat facets that intersect the frustoconical surface at a plurality of curved edges.

[0010] Embodiments may include one or more of the following features. The inner surface may be machined such that the lowest point of each curved edge is aligned with the boundary line between the upper portion and the lower portion. The inner surface may be machined such that the lowest point of each curved edge is above the boundary line between the upper portion and the lower portion. Joining may include one or more of adhering with an adhesive, coupling with a mechanical fastener, or fixing with a weld.

[0011] In another aspect, the retaining ring includes an annular body having an upper surface configured to be fixed to the carrier head, a bottom surface configured to contact the polishing surface, an outer surface extending from the upper surface around the outer upper periphery to the bottom surface around the outer bottom periphery, and an inner surface extending from the upper surface around the inner upper periphery to the bottom surface around the inner bottom periphery. The inner surface includes a plurality of regions that are angularly spaced around the annular body and have different surface textures.

[0012] Embodiments may include one or more of the following features. The plurality of regions may be arranged in a regular pattern. The different surface textures may include different roughnesses. The different roughnesses may include a first roughness having an Ra from 4 microinches to 64 microinches and a second roughness less than the first roughness. The different surface textures may include surface grooving in different directions. The different directions may be perpendicular. One of the different directions may be parallel or perpendicular to the inner bottom periphery. The different surface textures may include surface grooving having different depths.

[0013] In another aspect, the retaining ring includes an annular body having an upper surface configured to be fixed to the carrier head, a bottom surface configured to contact the polishing surface, an outer surface extending from the upper surface around the outer upper periphery to the bottom surface around the outer bottom periphery, and an inner surface extending from the upper surface around the inner upper periphery to the bottom surface around the inner bottom periphery. The inner surface includes a plurality of regions that are angularly spaced around the annular body and have different inclinations with respect to the bottom surface.

[0014] Embodiments may include one or more of the following features. The plurality of regions may be arranged in a regular pattern. One of the different inclinations may be perpendicular to the bottom surface. The different inclinations may include a first inclination that slopes inward from the bottom to the top and a second inclination that slopes outward from the bottom to the top.

[0015] Advantages may include the following. The edges of the polished substrate can contact the retaining ring at multiple points. Thus, the pressure on the substrate edge can be distributed over a wider area, improving the rotation of the substrate. As a result, the polished substrate can achieve better thickness uniformity, for example, an asymmetry with almost no angle. The retaining ring can have reduced wear and, as a result, a longer lifespan.

[0016] The details of one or more embodiments will be described in the accompanying drawings and the following description. Other aspects, features, and advantages will become apparent from these descriptions and drawings, as well as from the claims.

Brief Description of the Drawings

[0017]

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DETAILED DESCRIPTION OF THE INVENTION

[0018] Similar reference numerals in the drawings represent similar features.

[0019] The retaining ring within the CMP apparatus has an inner surface that restricts the movement of the substrate being polished by the CMP apparatus. In a conventional retaining ring, the inner surface has a circular outer perimeter. On the other hand, some embodiments of the retaining rings described herein have an inner surface formed by a plurality of planar facets, with adjacent facets joined at corners. Some embodiments of the retaining rings described herein have a serrated or meandering inner surface and / or an inner surface that includes alternative regions of different surface characteristics or different tilt angles. Thus, the uniformity of the thickness of the polished substrate can be improved.

[0020] Referring to FIG. 1, the retaining ring 100 is generally an annular ring that can be fixed to the carrier head 50 of a CMP apparatus. Suitable CMP apparatuses are described in U.S. Patent No. 5,738,574, and suitable carrier heads are described in U.S. Patent Nos. 6,251,215 and 6,857,945. The retaining ring 100 positions, centers, and fits within a load cup for holding in the transfer station of the CMP apparatus.

[0021] As an example, FIG. 1 shows a simplified carrier head 50 with a retaining ring 100 fixed to the top. The carrier head 50 includes a housing 52, a flexible membrane 54, a pressurizable chamber 56, and a retaining ring 100. The flexible membrane provides a mounting surface for the substrate 10. When the substrate 10 is mounted, the mounting surface can be in direct contact with the back surface of the substrate. In the example shown in FIG. 1, the membrane 54 is fixed between the retaining ring 100 and the housing 54, but in some embodiments, one or more other components, such as a clamping ring, etc., can be used to hold the membrane 54.

[0022] The pressurizable chamber 56 is located between the membrane 54 and the housing 52 and can be pressurized, for example, by using a fluid (gas or liquid), to push the front surface of the substrate 10 against the polishing surface 62 of a polishing pad 60 for polishing the front surface. In some embodiments, the pressure in the chamber 56, i.e., the downward pressure of the flexible membrane 54 onto the substrate 10, can be controlled using a pump (not shown) that is fluidly coupled to the chamber 56 through a passage in the housing.

[0023] The retaining ring 100 is fixed near the edge of the housing 52 to hold the substrate 10 under the membrane 54. For example, the retaining ring 100 can be fixed by a mechanical fastener 58, such as a screw or bolt, that extends through a passage 59 in the housing 52 into an aligned threaded receiving recess on the top surface of the retaining ring 100. Further, the top surface can have one or more alignment apertures arranged to mate with corresponding pins on the carrier head to enable correct alignment when the retaining ring 100 is fixed to the carrier head.

[0024] A drive shaft 80 can be provided for rotating and / or translating the carrier head 50 across the entire polishing pad 60. In some embodiments, the drive shaft 80 can be raised and lowered to control the pressure of the bottom surface of the retaining ring 100 against the polishing pad 60. Alternatively, the retaining ring 100 can be movable relative to the drive shaft 80, and the carrier head 50 can include a pressurizable internal chamber for controlling the downward pressure on the retaining ring 100, as described, for example, in U.S. Patent Nos. 6,183,354 or 7,575,504, which are incorporated herein by reference.

[0025] Referring to FIGS. 2 through 5, the upper surface 110 of the retaining ring 100 is substantially flat but includes a plurality of threaded recesses 112 for receiving fasteners for holding the retaining ring 100 to the carrier head. Optionally, the upper surface 110 can have one or more alignment features, such as apertures 114, arranged to mate with corresponding features, such as protrusions, on the carrier head to enable proper alignment when the retaining ring 100 is fixed to the carrier head. Optionally, the upper surface can include a raised outer rim where the recesses for the fasteners are located. Optionally, the upper surface can include a plurality of concentric ridges extending around the ring, for example, to grip the film 54.

[0026] The bottom surface 120 of the retaining ring 100 is configured to contact the polishing surface of the polishing pad. Optionally, the bottom surface 120 can include channels 122 that extend partially through the thickness of the retaining ring 100. In addition to the channels 122, the bottom surface 120 can be flat and parallel to the upper surface 110. In the example shown in FIGS. 2 through 5, the bottom surface 120 includes 18 channels 122, but can have a different number of channels, such as from 4 to 100. During operation, the channels 122 allow a polishing fluid, such as a slurry, which may or may not contain an abrasive, to flow under the retaining ring 100 to the substrate.

[0027] Channel 122 is generally linear and can extend from the inner surface 130 to the outer surface 140 of the retaining ring 100. The channels 122 can be distributed around the retaining ring 100 at equal angular intervals. The channels 122 are typically oriented at an angle α, e.g., from about 30° to about 60°, or about 45°, with respect to a radial segment (R) extending through the center of the retaining ring 100 and the channels, although alternatively the channels 122 can extend along the radial segment (R), i.e., at 0°.

[0028] Each channel 122 can have a width W (see FIG. 5) of from about 0.75 mm to about 25 mm, e.g., 3.125 mm. The ratio of the width of the channels to the width of the spacing between the channels can be from 10 / 90 to 50 / 50. The channels can have a uniform width along their radial length or can vary in width along their radial length, e.g., flare at the inner diameter and / or outer profile. All of the various channels 122 can have the same width profile or different channels can have different widths. The channels can be curved rather than linear segments.

[0029] The side walls 124 of the channels 122 can be perpendicular to the bottom surface 120 or can be at an angle less than 90°, e.g., from 45° to 85°, with respect to the bottom surface 120. In some configurations, the edge 126 where the side wall 124 intersects the bottom surface 120 has a radius of curvature or chamfer that is greater than about 0.1 mm but less than the height of the channel 122. The channels 122 can have a depth that is from 25% to 90% of the thickness of the lower portion 102 of the retaining ring (see FIG. 7).

[0030] The total thickness of the retaining ring 100, e.g., the thickness between the upper surface 110 and the bottom surface 120, can be from about 12.5 mm to about 37.5 mm.

[0031] Referring to FIGS. 2, 3 and 7, at least a part 142 of the outer surface 140 of the retaining ring 100 adjacent to the bottom surface 120 can be a vertical cylindrical surface having a circular shape in a plan view of the upper or bottom surface. In some embodiments, the retaining ring 100 includes an overhanging portion 145, and the bottom of the overhanging portion 145 defines a horizontal portion 146 of the outer surface 140. This horizontal portion 146 can assist in centering the retaining ring in the substrate loader or provide a lip for firmly stopping the retaining ring against the upper inner edge of the surrounding ring.

[0032] The outer surface 140 can include an inclined portion 144, for example, a frustum-shaped surface having an angle from the outside downward, that connects the vertical cylindrical portion 142 to the horizontal portion 146. A part 148 of the outer surface 140 of the retaining ring 100 adjacent to the upper surface 110 can be a vertical cylindrical surface. The cylindrical portion 148 of the outer surface 140 adjacent to the upper surface 110 can have a larger diameter than the cylindrical portion 142 adjacent to the bottom surface 120.

[0033] Referring to FIGS. 2, 3, 6 and 7, instead of a cylindrical surface, a part 132 of the inner surface 130 adjacent to the bottom surface 120 is formed by a plurality of facets 150. Each facet is a flat vertical surface and joins to an adjacent facet along a vertical edge 152. The flat vertical surface of each facet can be substantially perpendicular to the bottom surface 120. In some configurations, the vertical thickness of the part 132 is greater than the depth of the channel 122, as shown in FIG. 6.

[0034] The facets 150 intersect the bottom surface 120 along a straight lower edge 154. The straight edges 154 of the facets 150 along the bottom surface 120 are joined to each other at corners. Thus, in a plan view of the bottom, the joined lower edges 154 can form a polygon (the number of facets is so large that this polygonal structure cannot be seen in FIG. 5). The angle between each pair of adjacent facets can be the same, and the joined lower edges 154 form a regular polygon.

[0035] In the illustrated example, the portion 132 of the inner surface 130 has 72 facets 150. However, the retaining ring 100 could have from 10 to 150 facets. For example, the retaining ring 100 could have from 25 to 100 facets, such as from 60 to 80 facets. In some embodiments, the retaining ring 100 has 72 facets. The benefit of having approximately 72 facets appears to be providing excellent polishing uniformity.

[0036] In the illustrated example, each facet 150 has the same width (distance along the lower edge 154). However, in some embodiments, some of the facets have a different width than other facets. For example, the facets can be arranged with wider facets in a regular pattern, such as every other facet or every third facet, etc. Similarly, in the illustrated example, each facet 150 has the same height, but in some embodiments, some of the facets have a different height than other facets.

[0037] The number of facets 150 can be an integer multiple of the number of channels 122. For example, one channel 122 can be provided for every 2, 3, 4, or 5 facets on the inner surface 130. In some embodiments, each channel 122 on the bottom surface 120 intersects the inner surface 130 at an edge 152 between adjacent facets 150. Alternatively, each channel 122 on the bottom surface 120 can intersect the inner surface 130 in a region formed between the edges 152 that define a particular facet 150, i.e., the channel does not overlap the edge 152 between adjacent facets 150.

[0038] On average, the width of the bottom surface 120 of the retaining ring 100, i.e., the distance between the inner surface 130 and the outer surface 140, is from about 2.5 cm to about 5.0 cm.

[0039] A part 134 of the inner surface 130 located on the part 132 has a circular cross-section in a plane parallel to the bottom surface 120. This part 134 is adjacent to the upper surface 11 and can extend downward. This part 134 can be inclined, for example, to be a frustum-shaped surface with an angle from the outside downward.

[0040] Each flat facet 150 intersects the conical surface of the part 134 along the curved edge 156. In particular, the facets 150 are higher at the adjacent edges 152 than at their lateral centers, i.e., the places equidistant from the opposing edges 152. In short, the curved edge 156 descends away from each edge 152, and the lowest point is equidistant from the opposing edges 152 of the facet 150. Assuming that the surface 134 is frustum-shaped and the facets 150 are vertical, each curved edge 146 would define a hyperbola.

[0041] Returning to FIG. 1, the inner surface 130 of the retaining ring 100, together with the lower surface 240 of the flexible film 54, defines a substrate receiving recess 90. The retaining ring 100 prevents the substrate 10 from disengaging from the substrate receiving recess 90.

[0042] Generally, the substrate is circular and has a diameter of about 200 mm to about 300 mm. To enable the position of the substrate 10 to be moved relative to the retaining ring 100, the size of the recess 90 in the top view or bottom view is generally larger than the area of the substrate 10. For the purpose of discussion, the inner radius (IR) of the retaining ring 100 is defined as the distance between the center C of the retaining ring 100 and the center point of the facet 150 that is equidistant between two opposing edges 152 in the plan view of the retaining ring. The inner diameter (twice the inner radius IR) is slightly larger than the substrate radius, for example, about 1 - 5 mm larger. For example, for a substrate with a diameter of 300 mm, the retaining ring can have an inner diameter of about 301 - 305 mm.

[0043] During the polishing process, the carrier head 50 including the holding ring 100 moves relative to the polishing pad 60. The friction of the polishing pad 60 against the substrate 10 presses the substrate 10 against the inner surface 130 of the holding ring 100. Due to the faceted structure, for at least some period of time, the substrate 10 contacts at least two facets 150 of the inner surface 130.

[0044] However, since the radius of the substrate 10 is smaller than the radius of the inner surface 130 of the holding ring 100, the substrate 10 and the inner surface 130 have different angular velocities. As a result, the pair of (or set of, etc.) facets 150 that contact the substrate 10 will shift over time. In short, the holding ring 100 rotates relative to the substrate 10.

[0045] The wear of the inner surface 130 of the holding ring 100 can be reduced or evenly distributed around the holding ring compared to a holding ring having a cylindrical inner surface that contacts the substrate 10. Without being limited to any particular theory, when the inner surface of the holding ring is cylindrical, a substrate having a circular outer perimeter contacts the inner surface at a single location. In contrast, multiple contact points can more widely distribute the force of the substrate 10 against the inner surface 130, thus reducing the total force and wear at any particular point. The reduction in wear can extend the service life of the holding ring.

[0046] Again, without being limited to any particular theory, during the relative movement between the holding ring 100 and the substrate 10, the substrate does not make direct point-to-point contact with either the channel 122 or the channel opening located at the edge 152 between the facets 150. Generally, in the holding ring 100, the channel 122 can form a high-stress region where the holding ring tends to be more easily damaged or broken than other parts of the ring. To remove the direct point-to-point contact between the channel 122 and the substrate 10, the high-stress region can be protected from the direct influence of the substrate 10 and the likelihood of damage to the holding ring can be reduced. As a result, the wear of the holding ring is reduced and the holding ring can be used for a long period of time.

[0047] In some polishing processes, the relative movement between the substrate 10 and the retaining ring 100 can reduce the asymmetry of the polished substrate and improve the uniformity within the wafer. A polished substrate having asymmetry has thickness variations that vary with angular coordinates. Without being limited to any particular theory again, multiple contacts between the substrate 10 and the retaining ring 100 can rotate the substrate 10 relative to the carrier head 50 compared to a single contact situation, and thus angularly disperse the influence of any asymmetric pressure distribution from the carrier head 50, thereby reducing the likelihood of asymmetry occurring or the amount of asymmetry.

[0048] At least the lower surface 102 of the retaining ring 100 including the bottom surface 120 can be formed of a material that is chemically inert to the CMP process. The material should have sufficient elasticity such that no chips or cracks occur in the substrate even if the substrate edge contacts the retaining ring 100. However, the material should not have so much elasticity that it is pushed into the substrate receiving recess when the carrier head applies downward pressure to the retaining ring 100. The material of the lower portion 102 should have a low wear rate and be durable although it is acceptable for the lower portion 102 of the retaining ring 100 to wear.

[0049] For example, the lower portion 102 of the retaining ring 100 can be made of a plastic that is chemically inert in the CMP process. The plastic may have a durometer measurement of about 80 - 95 on a Shore D hardness scale. Generally, the elastic modulus of the plastic is about 0.3 - 1.0x10 6It can be in the range of psi. Suitable plastics can include polyphenylene sulfide (PPS), polyaryl ether ketone (PAEK), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE), polybenzimidazole (PBI), polyetherimide (PEI), polyether ketone ketone (PEKK), polybutylene naphthalene (PBN), polyvinyl chloride (PVC), polycarbonate, one or a combination of more than one of these plastics, or a composite material including one or more of these plastics and a filler such as, for example, glass or carbon fiber (for example, it can consist of these). The advantage of polyphenylene sulfide (PPS) is that it is highly reliable and is often used as the material for the retaining ring.

[0050] The upper part 104 of the retaining ring 100 can be made of a material with at least the same rigidity as the lower part 102. In some embodiments, the upper part 104 can be made of a material more rigid than the lower part 102. For example, the upper part 104 can be a metal such as aluminum or stainless steel, a ceramic material, or a plastic more rigid than the plastic of the lower part 102. In some embodiments, the upper part 104 has the same rigidity as the lower part, for example, within 2%, but has low quality, such as a large proportion of internal defects such as contaminants, inclusions or voids, and thus is inexpensive.

[0051] For example, an adhesive such as epoxy can be used to join the lower part 102 to the upper part 104. Alternatively or in addition, mechanical fasteners and / or joints can be used to join the lower part 102 to the upper part 104.

[0052] In some embodiments, the lowest point on the curved edge 156 between the facet 150 and the inner conical portion 134 can be aligned as the boundary line between the upper ring 104 and the lower ring 102, i.e., can be at the same height. However, in some embodiments, the lowest point on the curved edge 156 is on the boundary line between the upper ring 104 and the lower ring 102.

[0053] To manufacture the retaining ring, the upper ring 104 can be formed with a frustoconical inner surface 134, and the lower ring 102 can be formed with a vertical cylindrical surface. The lower ring 102 is joined to the upper ring 104. Next, the inner surface 130 is machined to form the facet 150. The upper ring 104 and the lower ring 102 can be formed by machining a suitable block of material or by injection molding.

[0054] The retaining ring 100 can alternatively have one or more other features instead of those described above. In some embodiments, the retaining ring 100 has one or more through-holes that extend horizontally from the inner surface to the outer surface or at a small angle from horizontal through the retaining ring body so as to allow a fluid, such as a gas or a liquid, to pass from the inside to the outside or from the outside to the inside of the retaining ring during polishing. The through-holes can be evenly spaced around the retaining ring.

[0055] In some embodiments, one or more surfaces of the retaining ring, such as the inner surface 130 and / or the outer diameter surface 140, can be coated with a film. The film can be a hydrophobic or hydrophilic film and / or can function as a protective film. For example, the film can be made of carbon such as polytetrafluoroethylene (PTFE) or diamond.

[0056] In addition to the flat facet type regular polygons described with reference to FIGS. 1 to 7, the inner surface of the retaining ring can have other shape dimensions. For example, referring to FIGS. 8 to 12, the inner surface 130 of the retaining ring can have a plurality of inwardly extending protrusions 200. The protrusions can extend from a circle having a first radius R1 to a circle having a smaller second radius R2 inwardly (shown in FIG. 8). Examples of the shape dimensions of the inner surface 130 include zigzag, serrated, trapezoidal, sine wave, but other shape dimensions are also possible. There can be 7 to 150 protrusions spaced apart around the inner circumference of the retaining ring. The protrusions can be arranged at equiangular intervals around the retaining ring. Alternatively, the spacing between the protrusions can be changed, for example, in a regular pattern.

[0057] For example, as shown in FIGS. 8 to 10, for some embodiments, each protrusion can join at its edge to the immediately adjacent protrusion. For example, the region between each pair of adjacent protrusions can not include a flat surface or an arcuate surface that substantially contacts the circle defined by the first radius R1. FIG. 8 shows the protrusion as a triangle, but other shape dimensions such as trapezoid (shown in FIG. 10), sine wave (shown in FIG. 12), and semi - circle are possible. In addition, the inner tip of each protrusion and / or the intersection between each protrusion can be rounded.

[0058] As shown in FIGS. 9 to 11, for some embodiments, the innermost part of each protrusion 200 can be a flat surface 202, such as a flat facet, at the inner second radius R2. For example, referring to FIG. 9, the protrusion 200 forms a serrated shape dimension having a flat surface 202 and a flat side surface 206. The innermost flat or curved region 204 can separate each protrusion 200 at the outer first radius R1. For the serrated shape dimension, each flat surface 202 can intersect its adjacent flat side surface 206 at an angle of about 90°, for example, at an angle of 85 - 90°.

[0059] Referring to FIGS. 10 and 11, the protrusion 200 is trapezoidal with a flat inner surface 202 and a flat side surface 206. For the trapezoidal protrusion 200, the angle between the flat inner surface 202 and the flat side surface 206 can be 115 - 145°. In FIG. 10, the protrusion 200 is separated by a flat or curved region 204 at the outer first radius R1, while in FIG. 11, each protrusion 200 is joined to the immediately adjacent protrusion at the edge of the protrusion even without the flat or curved region 204.

[0060] Referring to FIG. 12, the protrusion 200 can form a wavy surface. For example, the bottom inner edge can form a meandering path. Each protrusion can be substantially sinusoidal. A potential advantage of this embodiment is that since there are no acute angles between the protrusions, the possibility of slurry adhering or drying at the corners is reduced, and thus the possibility of defects being reduced.

[0061] Referring to FIG. 13, portions of the inner surface 130 can have different surface textures such as different surface roughnesses, or surface grooving in different directions such as vertical to horizontal grooving, or surface grooving with different depths. For example, the inner surface 130 can include an arcuate segment 210 having a different surface texture from the arcuate segment 212. In some embodiments, the portions having different surface textures, such as arcuate segments, are arranged in a regular pattern, for example, an alternating pattern such as smooth and rough alternating, or horizontal and vertical grooving alternating. There can be 7 to 150 portions spaced around the inner circumference of the retaining ring. The portions can be arranged at equal angular intervals around the retaining ring. Alternatively, the spacing between the portions can be changed, for example, in a regular pattern. Each portion can have the same arcuate length, but this is not essential.

[0062] For example, the arcuate segment 212 may be rougher than the arcuate segment 210. For example, while the arcuate segment 212 has a Ra roughness of 4 to 2000 microinches, for example 8 to 64 microinches, the arcuate segment 210 may have a Ra roughness that drops to about 2 microinches or less.

[0063] As another example, referring to FIG. 14, the arcuate segment 212 can have grooving in a direction different from that of the arcuate segment 210. The grooving direction of the arcuate segment 212 can be perpendicular to the grooving direction of the arcuate segment 210, while other angles, for example, 20 to 90°, are also possible. For example, as shown in FIG. 14, in some embodiments, the arcuate segments 210, 212 alternate between horizontal grooving and vertical grooving. However, other orientations are possible, for example, alternating between diagonally left and diagonally right. In addition, more complex patterns of three or more surface textures are possible.

[0064] The different surface textures described above can be applied to the facets 150 or protrusions 200 of the above embodiments. Thus, the different facets 150 and protrusions 200 can have different surface textures, for example, different surface roughnesses, or surface grooving in different directions. Also, in some embodiments, facets or protrusions having different surface textures are arranged in a regular pattern, for example, an alternating pattern such as smooth and rough alternating, or horizontal grooving and vertical grooving alternating.

[0065] In the various embodiments described above, the portion 132 of the inner surface 130 adjacent to the bottom surface 120 is perpendicular (perpendicular to the polished surface), but this portion 132 of the inner surface 130 could be inclined at an angle, for example, up to 30° from perpendicular.

[0066] In addition, referring to FIG. 15, the portion 132 of the inner surface 130 adjacent to the bottom surface 120 can have portions with different inclinations. For example, the inner surface 130 can include a facet or arcuate segment 220 having an inclination angle different from that of the facet or arcuate segment 222 with respect to the horizontal plane. In some embodiments, for example, portions such as facets or arcuate segments are arranged in a regular pattern such as an alternating pattern. For example, as shown in FIG. 15, while the facet or arcuate segment 220 inclines outward (from the bottom to the top), the facet or arcuate segment 222 inclines inward (from the bottom to the top). However, other combinations are possible, such as, for example, vertical vs. inclined, or small inclination angle vs. large inclination angle. There can be 7 to 150 portions spaced around the inner surface of the retaining ring. The portions can be arranged at equal angular intervals around the retaining ring, or the spacing between the portions can be varied, for example, in a regular pattern or the like.

[0067] The different inclination angles of the above surfaces can be applied to the facets 150 or protrusions 200 of the above embodiments. Thus, the different facets 150 and protrusions 200 can have different inclination angles. The change in the inclination angle can also be combined with the change in the surface texture.

[0068] Referring to FIG. 16, a part of the retaining ring having the inner surface 132 in contact with the substrate can be the insertion portion 106 that fits into the recess of the ring 108 extending above and radially outside the insertion portion 106. When the inner surface 132 becomes damaged or worn due to long-term use, the insertion portion 106 can be replaced with a new insertion portion 106.

[0069] The retaining ring can be formed from two or more stacked regions of different materials or can be a single ring of a homogeneous composition such as a solid plastic ring. When present, the channels can be aligned at the normal points of the features or different channels can intersect at different points over the features. When present, the channels can cover a range from 5% to 90% of the bottom surface of the retaining ring. The outer surface of the retaining ring can include steps or lips or can be a single vertical cylindrical or frustoconical surface. This concept is applicable to retaining rings of different sizes, such as for substrates with diameters of 4 to 18 inches or more.

[0070] A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. a top surface configured to be secured to a carrier head; a bottom surface configured to contact the polishing surface; an outer surface extending from the top surface of an outer top perimeter to the bottom surface of an outer bottom perimeter; an inner surface extending from said top surface of an inner top perimeter to said bottom surface of an inner bottom perimeter, the inner surface comprising a first portion adjacent said bottom surface and a second portion adjacent said first portion along a boundary line, the first portion comprising seven or more planar facets, adjacent planar facets being joined by straight side edges, and the inner bottom perimeter defined by straight bottom edges of the planar facets, the second portion including a frustoconical surface sloping downwardly from the outside; An annular body including A retaining ring comprising:

2. 2. The retaining ring of claim 1, wherein the perimeter includes a plurality of curved edges, each curved edge for a facet having a lowest point at a horizontal center of the facet.

3. The retaining ring of claim 2 , wherein said annular body includes an upper portion and a lower portion of a different material than said upper portion.

4. The retaining ring of claim 3 , wherein the lowest point of each curved edge is aligned with the boundary line between the upper and lower portions.

5. The retaining ring of claim 1 , wherein the bottom surface comprises a channel extending from the outer surface to the inner surface.

6. The retaining ring of claim 5 , wherein each channel has an end that opens onto the inner surface of the annular body with straight side edges.

7. 7. The retaining ring of claim 6, wherein said inner surface comprises a first number of facets and said bottom surface comprises a second number of channels, said first number being an integer multiple of said second number.

8. 8. The retaining ring of claim 7, wherein the integer is 3, 4, or 5.

9. The retaining ring of claim 1 , wherein the inner surface comprises between 10 and 150 facets.

10. The retaining ring of claim 9 , wherein the inner surface comprises between 60 and 80 facets.

11. The retaining ring of claim 10 , wherein the inner surface comprises a total of 72 facets.

12. The retaining ring of claim 1 , wherein said inner bottom perimeter is a regular polygon.

13. The retaining ring of claim 1 , wherein each planar facet intersects the frustoconical surface along a hyperbola.

14. The retaining ring of claim 1 , wherein each planar facet is substantially perpendicular to the bottom surface.

15. 1. A method of forming a retaining ring, comprising: joining an upper portion of the retaining ring having an inner frusto-conical surface to a lower portion of the retaining ring having an inner cylindrical surface; machining the inner surface of the lower portion and the inner surface of the upper portion to form a plurality of flat facets intersecting the frusto-conical surface at a plurality of curved edges; The method includes:

16. 16. The method of claim 15, comprising machining the inner surface of the lower ring and the inner surface of the upper portion so that a lowest point on each curved edge is aligned with a boundary line between the upper and lower surfaces.

17. 16. The method of claim 15, including machining the inner surface of the lower ring and the inner surface of the upper portion so that a lowest point on each curved edge is on a boundary line between the upper and lower portions.

18. The method of claim 15 , wherein joining comprises one or more of adhesively adhering, joining with mechanical fasteners, or fastening with a dovetail joint.

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