阅读说明：本技术 内表面具有特征结构的保持环 (Retaining ring with features on the inner surface ) 是由 史蒂芬·马克·雷迪 西蒙·亚沃伯格 吴正勋 史蒂文·M·苏尼加 安德鲁·J·纳甘盖斯特 塞 于 2016-05-27 设计创作，主要内容包括：保持环的一些实施方式具有内表面,所述内表面具有由多个平面刻面形成的第一部分和沿边界邻接第一部分的第二部分,并且保持环包括从外部朝内向下倾斜的截头圆锥形表面。保持环的一些实施方式具有锯齿状内表面或蜿蜒内表面和/或具有不同表面性质或不同倾斜角的交替区域的内表面。(Some embodiments of the retaining ring have an inner surface having a first portion formed by a plurality of planar facets and a second portion bordering the first portion along a boundary, and the retaining ring includes a frustoconical surface sloping inwardly from the exterior. Some embodiments of the retaining ring have a serrated or serpentine inner surface and/or an inner surface having alternating regions of different surface properties or different inclination angles.)

1. A retaining ring for a carrier head for polishing a substrate in the manufacture of integrated circuits, the retaining ring comprising:

an annular body comprising

A top surface configured to be secured to a carrier head;

a bottom surface configured to contact a polishing surface;

an outer surface extending from the top surface at an outer top perimeter to the bottom surface at an outer bottom perimeter; and

an inner surface extending from the top surface at an inner top perimeter to the bottom surface at an inner bottom perimeter, the inner surface comprising a first portion adjacent to the bottom surface and a second portion bordering the first portion along a boundary, wherein the first portion of the inner surface comprises between 10 and 150 planar facets, wherein adjacent planar facets of the first portion of the inner surface are connected at straight side edges and the inner bottom perimeter defined by straight bottom edges of the planar facets forms a regular polygon, wherein the retaining ring has an inner diameter of about 301mm to 305mm, and wherein the second portion comprises a frustoconical surface sloping inwardly from the exterior.

2. The retaining ring of claim 1, wherein the boundary comprises a plurality of curved edges and has a lowest point at a horizontal center of the facet for each curved edge of a facet.

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

4. The retaining ring of claim 5, wherein each channel includes an end that is open to the inner surface of the body at one of the straight side edges.

5. The retaining ring of claim 1, wherein the first portion of the inner surface includes between 60 and 80 facets.

6. The retaining ring of claim 1, wherein each planar facet intersects the frustoconical surface along an edge forming a hyperbola.

7. A retaining ring, comprising:

an annular body comprising

A top surface configured to be secured to a carrier head;

a bottom surface configured to contact a polishing surface;

an outer surface extending from the top surface at an outer top perimeter to the bottom surface at an outer bottom perimeter; and

an inner surface extending from the top surface at an inner top perimeter to the bottom surface at an inner bottom perimeter, the inner surface comprising a plurality of inwardly extending projections, each projection having a flat innermost surface.

8. The retaining ring of claim 1, wherein the protrusion comprises a trapezoidal protrusion.

9. The retaining ring of claim 2, wherein the angled sides of adjacent trapezoidal shaped projections directly abut.

10. A retaining ring, comprising:

an annular body comprising

A top surface configured to be secured to a carrier head;

a bottom surface configured to contact a polishing surface;

an outer surface extending from the top surface at an outer top perimeter to the bottom surface at an outer bottom perimeter; and

an inner surface extending from the top surface at an inner top perimeter to the bottom surface at an inner bottom perimeter, the inner surface comprising a plurality of regions angularly spaced around the ring shaped body, the plurality of regions having different surface textures.

11. The retaining ring of claim 10, wherein the plurality of regions are arranged in a regular pattern.

12. The retaining ring of claim 10, wherein the different surface textures comprise different roughnesses.

13. The retaining ring of claim 10, wherein the different surface textures comprise surface kerfs in different directions.

14. The retaining ring of claim 10, wherein the different surface textures comprise surface kerfs having different depths.

15. A retaining ring, comprising:

an annular body comprising

A top surface configured to be secured to a carrier head;

a bottom surface configured to contact a polishing surface;

an outer surface extending from the top surface at an outer top perimeter to the bottom surface at an outer bottom perimeter; and

an inner surface extending from the top surface at an inner top perimeter to the bottom surface at an inner bottom perimeter, the inner surface comprising a plurality of regions angularly spaced around the ring shaped body, the plurality of regions having different inclinations relative to the bottom surface.

16. The retaining ring of claim 15, wherein the plurality of regions are arranged in a regular pattern.

17. The retaining ring of claim 15, wherein one of the different inclinations is perpendicular to the bottom surface.

18. The retaining ring of claim 15, wherein the different inclinations include a first inclination that is inwardly inclined from bottom to top and a second inclination that is outwardly inclined from bottom to top.

Technical Field

The present disclosure relates generally to chemical mechanical polishing of substrates, and more particularly to a retaining ring for use in chemical mechanical polishing.

Background

Integrated circuits are typically formed on a silicon substrate by the sequential deposition of conductive, semiconductive, or insulative layers on the substrate. One fabrication step involves depositing a filler layer over the non-planar surface and planarizing the filler layer until the non-planar surface is exposed. For example, a conductive filler layer can be deposited on a patterned insulating layer to fill trenches or holes in the insulating layer. The filler layer is then polished until the raised pattern of the insulating layer is exposed. After planarization, the portions of the conductive layer left between the raised patterns of the insulative layer form vias (via), plugs, and lines that provide conductive paths between thin film circuits on the substrate. In addition, planarization may be required to planarize the dielectric layer at the substrate surface for photolithography.

Chemical Mechanical Polishing (CMP) is a well-established planarization method. Such planarization methods typically require that the substrate be mounted on a carrier head or polishing head of the CMP apparatus. The exposed surface of the substrate is placed against a rotating polishing disk pad (rotating polishing disk pad) or tape pad. The polishing pad can be a "standard" pad or a fixed abrasive pad. The standard pad has a durable roughened surface, while the fixed abrasive pad has abrasive particles held in a containment medium. The carrier head provides a controllable load on the substrate to urge the carrier head against the polishing pad. A polishing slurry comprising at least one chemically-reactive agent and abrasive particles (if a standard pad is used) are supplied to the surface of the polishing pad.

The substrate is typically held under the carrier head by a retaining ring. However, because the retaining ring contacts the polishing pad, the retaining ring tends to wear and occasionally be replaced. Some retaining rings have an upper portion formed of metal and a lower portion formed of wear-resistant plastic, while some are a single plastic component.

Disclosure of Invention

In one aspect, a retaining ring includes an annular body having: a top surface configured to be secured to a carrier head; a bottom surface configured to contact a polishing surface; an outer surface extending from a top surface at an outer top perimeter to a bottom surface at an outer bottom perimeter; and an inner surface extending from the top surface at the inner top perimeter to the bottom surface at the inner bottom perimeter. The inner surface includes a first portion adjacent the bottom surface and a second portion adjoining the first portion along a boundary. The first portion includes seven or more facets (facets). The inner bottom perimeter is defined by the bottom edges of the facets. The second portion may comprise a frusto-conical (frustoconical) surface sloping downwardly from the exterior inwardly.

Implementations may include one or more of the following features. The facet may be planar. Adjacent facets may be connected at straight side edges. The inner bottom perimeter may be defined by a straight bottom edge of the planar facet. The boundary may include a plurality of curved edges corresponding to the plurality of facets, and each curved edge of a facet may have a lowest point at a horizontal center of the facet. The annular body may include an upper portion and a lower portion of a different material than the upper portion. The lowest point on each curved edge may be aligned to the boundary between the upper and lower portions. The bottom surface may include a channel extending from the outer surface to the inner surface. Each channel may have an end that is open to the inner surface of the body at the straight side edge. The inner surface may include a first number of facets and the bottom surface may have a second number of channels, and the first number may be an integer multiple of the second number. The integer may be three, four or five. The inner surface may have a total of 72 facets. The inner bottom perimeter may be a regular polygon.

In another aspect, a retaining ring includes an annular body having: a top surface configured to be secured to a carrier head; a bottom surface configured to contact a polishing surface; an outer surface extending from a top surface at an outer top perimeter to a bottom surface at an outer bottom perimeter; and an inner surface extending from the top surface at the inner top perimeter to the bottom surface at the inner bottom perimeter. The inner surface includes a plurality of inwardly extending projections, each projection having a planar innermost surface.

In another aspect, a retaining ring includes an annular body having: a top surface configured to be secured to a carrier head; a bottom surface configured to contact a polishing surface; an outer surface extending from a top surface at an outer top perimeter to a bottom surface at an outer bottom perimeter; and an inner surface extending from the top surface at the inner top perimeter to the bottom surface at the inner bottom perimeter. The inner surface includes a plurality of inwardly extending projections that provide an inner bottom perimeter having a serpentine path (serpentine path).

In another aspect, a method of forming a retaining ring includes: joining an upper portion of a retaining ring having a frustoconical inner surface to a lower portion of a 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 intersecting the frustoconical surface at a plurality of curved edges.

Implementations may include one or more of the following features. The inner surface may be machined so that the lowest point on each curved edge is aligned to the boundary between the upper and lower portions. The inner surface may be machined such that the lowest point on each curved edge is above the boundary between the upper and lower portions. Joining may include one or more of bonding with an adhesive, joining with a mechanical fastener, or securing with a dovetailed joint.

In another aspect, a retaining ring includes an annular body having: a top surface configured to be secured to a carrier head; a bottom surface configured to contact a polishing surface; an outer surface extending from a top surface at an outer top perimeter to a bottom surface at an outer bottom perimeter; and an inner surface extending from the top surface at the inner top perimeter to the bottom surface at the inner bottom perimeter. The inner surface includes a plurality of regions angularly spaced around the annular body, the plurality of regions having different surface textures.

Implementations 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 a Ra between 4 and 64 microinches and a second roughness less than the first roughness. The different surface textures may comprise surface grooving in different directions. The different directions may be vertical. One of the different directions may be parallel or perpendicular to the inner bottom perimeter. The different surface textures may include surface grooves having different depths.

In another aspect, a retaining ring includes an annular body having: a top surface configured to be secured to a carrier head; a bottom surface configured to contact a polishing surface; an outer surface extending from a top surface at an outer top perimeter to a bottom surface at an outer bottom perimeter; and an inner surface extending from the top surface at the inner top perimeter to the bottom surface at the inner bottom perimeter. The inner surface includes a plurality of regions angularly spaced about the annular body, the plurality of regions having different inclinations relative to the bottom surface.

Implementations 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 slopes may include a first slope that slopes inwardly from bottom to top and a second slope that slopes outwardly from bottom to top.

Advantages may include the following. Which of the edges of the substrate being polished contact the retaining ring at multiple points. Therefore, the pressure on the edge of the substrate can be distributed over a wider area, or the rotation of the substrate can be improved. Thus, polishing the substrate can achieve better thickness uniformity (e.g., less angular asymmetry). The retaining ring may experience lower wear and therefore have a longer life.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

Drawings

Fig. 1 is a schematic cross-sectional view of a carrier head.

Fig. 2 is a schematic top perspective view of a retaining ring.

Fig. 3 is a schematic bottom perspective view of the retaining ring of fig. 2.

Fig. 4 is a schematic plan top view of the retaining ring of fig. 2.

Fig. 5 is a schematic bottom plan view of the retaining ring of fig. 2.

Fig. 6 is a schematic close-up perspective view of the retaining ring of fig. 2.

Fig. 7 is a schematic cross-sectional side view of the retaining ring of fig. 2.

Fig. 8-12 are schematic cross-sectional plan views of a portion of a retaining ring having an inner surface with other geometries.

FIG. 13 is a schematic cross-sectional plan view of a portion of a retaining ring having an inner surface with different surface texture regions.

FIG. 14 is a schematic perspective view of a portion of a retaining ring having an inner surface with areas of different surface texture.

Fig. 15 is a schematic perspective view of a portion of a retaining ring having an inner surface with a different inclination.

Fig. 16 is a schematic cross-sectional side view of a retaining ring having an insert to provide an inner surface in contact with a substrate.

Like reference symbols in the various drawings indicate like features.

Detailed Description

A retaining ring in a CMP apparatus has an inner surface that constrains movement of a substrate to be polished by the CMP apparatus. In conventional retaining rings, the inner surface has a circular perimeter. In contrast, some embodiments of the retaining rings described herein have an inner surface formed from a plurality of planar facets, with adjacent facets joined at corners. Some embodiments of the retaining rings described herein have a serrated or serpentine inner surface and/or an inner surface with alternating regions of different surface properties or different tilt angles. This can improve the thickness uniformity of the polished substrate.

Referring to fig. 1, the retaining ring 100 is generally an annular ring that can be secured to a carrier head 50 of a CMP apparatus. Suitable CMP apparatus are described in U.S. patent No. 5,738,574, and suitable carrier heads are described in U.S. patent No. 6,251,215 and U.S. patent No. 6,857,945. The retaining ring 100 fits into the load cup to position, center, and hold the substrate at the transfer station of the CMP apparatus.

By way of example, FIG. 1 shows a simplified carrier head 50 with a retaining ring 100 secured thereto. Carrier head 50 includes housing 52, flexible membrane 54, pressurization chamber 56, and retaining ring 100. The flexible film provides a mounting surface for the substrate 10. When the substrate 10 is mounted, the mounting surface may directly contact the back surface of the substrate. In the example shown in fig. 1, the membrane 54 is clamped between the retaining ring 100 and the housing 52, but in some embodiments, one or more other components (e.g., a clamping ring) may be used to retain the membrane 54.

A pressurization chamber 56 is located between the membrane 54 and the housing 52, which may be pressurized, for example, with a fluid (gas or liquid) to urge the front surface of the substrate 10 against the polishing surface 62 of the polishing pad 60 to polish the front surface. In some embodiments, the pressure in the chamber 56, and thus the downward pressure of the flexible membrane 54 on the substrate 10, may be controlled using a pump (not shown) fluidly connected to the chamber 56 through a passage in the housing.

A retaining ring 100 is secured near the edge of the housing 52 to restrain the substrate 10 under the membrane 54. For example, the retaining ring 100 may be secured by mechanical fasteners 58 (e.g., screws or bolts) that extend through the passages 59 in the housing 52 into aligned threaded receiving grooves in the top surface of the retaining ring 100. In addition, the top surface may have one or more alignment holes positioned to mate with corresponding pins on the carrier head to allow proper alignment when securing the retaining ring 100 to the carrier head.

A drive shaft 80 can be provided to rotate and/or translate (translate) the carrier head 50 across the 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 may be movable relative to the drive shaft 80, and the carrier head 50 may include an internal chamber that may be pressurized to control the downward pressure on the retaining ring 100, for example as described in U.S. patent No. 6,183,354 or No. 7,575,504.

Referring to fig. 2-5, the top surface 110 of the retaining ring 100 is largely flat, but includes a plurality of threaded grooves 112 to receive fasteners to hold the retaining ring 100 to the carrier head. Optionally, the top surface 110 can have one or more alignment features (e.g., grooves 114) positioned to mate with corresponding features (e.g., protrusions) on the carrier head to allow proper alignment when securing the retaining ring 100 to the carrier head. Optionally, the top surface may include a raised outer edge at which the recess of the fastener is seated. Optionally, the top surface may include a plurality of concentric ridges that extend around the ring, for example, to grip the membrane 54.

The bottom surface of the retaining ring 100 is configured to contact the polishing surface of the polishing pad. Optionally, the bottom surface 120 may include a channel 122 that extends partially through the thickness of the retaining ring 100. The bottom surface 120 may be flat and may be parallel to the upper surface 110, except for the channel 122. In the example shown in fig. 2-5, the bottom surface 120 includes eighteen channels 122, but there may be a different number of channels (e.g., four to one hundred channels). In operation, the channel 122 allows a polishing fluid (such as a slurry), which may include abrasives or be abrasive-free, to flow beneath the retaining ring 100 to the substrate.

The channel 122 may be substantially straight and extends from the inner surface 130 to the outer surface 140 of the retaining ring 100. The channels 122 may be distributed at equal angular intervals around the retaining ring 100. The channel 122 is generally oriented at an angle α (e.g., between about 30 ° and about 60 °, or about 45 °) relative to a radial segment (R) that extends through the center of the retaining ring 100 and the channel, but alternatively the channel 122 may extend along the radial segment (R) (i.e., 0 ° angle).

Each channel 122 may have a width W (see fig. 5) of about 0.75mm to about 25mm (e.g., about 3.125 mm). The ratio of the channel width to the space width between the channels may be between 10/90 and 50/50. The channels may have a uniform width along the radial length, or may vary in width along the radial length, such as flaring at the inner and/or outer diameters (flared). The various channels 122 may all have the same width profile, or different channels may have different widths. The channel may be curved rather than a linear section.

The sidewalls 124 of the channel 122 may be perpendicular to the bottom surface 120, or may be angled less than 90 ° relative to the bottom surface 120 (e.g., at an angle of 45-85 °). In some configurations, the edge 126 where the sidewall 124 intersects the bottom surface 120 has a radius of curvature or chamfer (chamfer) that is greater than about 0.1mm, but less than the height of the channel 122. The channel 122 may have a depth of between 25% and 90% of the thickness of the lower portion 102 of the retaining ring (see fig. 7).

The retaining ring 100 may have an overall thickness (e.g., between the top surface 110 and the bottom surface 120) of about 12.5mm to about 37.5 mm.

Referring to fig. 2, 3, and 7, in either a top or bottom plan view, at least a portion 142 of the outer surface 140 of the retaining ring 100 adjacent the bottom surface 120 may be a vertical cylindrical surface having a circular shape. In some embodiments, the retaining ring 100 includes an overhang portion 145; the bottom of the overhang portion 145 defines a horizontal portion 146 of the outer surface 140. This horizontal portion 146 may provide a lip to help center the retaining ring in the substrate loader or provide a hard stop (hard stop) for the retaining ring against the top inner edge of the surrounding ring.

The outer surface 140 may include an inclined portion 144 (e.g., a frustoconical surface that slopes inwardly from the outside) that connects the vertical cylindrical portion 142 to the horizontal portion 146. The portion 148 of the outer surface 140 of the retaining ring 100 adjacent to the top surface 110 may be a vertical cylindrical surface. The cylindrical portion 148 of the outer surface 140 adjacent the top surface 110 may have a larger diameter than the cylindrical portion 142 adjacent the bottom surface 120.

Referring to fig. 2, 3, 6, and 7, the portion 132 of the inner surface 130 adjacent to the bottom surface 120 is formed by a plurality of facets 150, rather than a cylindrical surface. Each facet is a flat vertical surface and joins adjacent facets along a vertical edge 152. The flat vertical surface in each facet may be substantially perpendicular to the bottom surface 120. In some configurations, the thickness of portion 132 in the vertical direction is greater than the depth of channel 122, as shown in fig. 6.

The facet 150 intersects the bottom surface 120 along a straight lower edge 154. The straight edges 154 of the facets 150 along the bottom surface 120 connect to each other at the corners. Thus, in bottom plan view, the connected lower edges 154 may form a polygon (the number of facets is sufficient so that this polygonal structure is not visible in fig. 5). The angle between each pair of adjacent facets may be the same such that the connected lower edges 154 form a regular polygon.

In the example shown, the portion 132 of the inner surface 130 has seventy-two facets 150. However, the retaining ring 100 may have ten to one hundred fifty facets. For example, the retaining ring 100 may have twenty-five to one hundred facets (e.g., sixty to eighty facets). In some embodiments, the retaining ring 100 has seventy-two facets. An advantage of having about seventy-two facets is that it appears to provide superior polishing uniformity.

In the example shown, each facet 150 has the same width (distance along lower edge 154). However, in some embodiments, some facets have a different width than other facets. For example, the facets may be arranged with wider facets arranged in a regular pattern (e.g., every other facet or every third facet). Likewise, in the example shown, each facet 150 has the same height, but in some embodiments, some facets have different heights than other facets.

The number of facets 150 may be an integer multiple of the number of channels 122. For example, one channel 122 may be provided for every two, three, four, or five facets 150 on the inner surface 130. In some embodiments, each channel 122 in the bottom surface 120 intersects the inner surface 130 at an edge 152 between adjacent facets 150. Alternatively, each channel 122 in the bottom surface 120 may intersect the inner surface 130 in the region formed between the edges 152 defining a particular facet 150, i.e., the channel does not overlap the edges 152 between adjacent facets 150.

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 about 2.5Gm to about 5.0 Gm.

A portion 134 of the inner surface 130 above the portion 132 has a circular cross-section in a plane parallel to the bottom surface 120. This portion 134 may be adjacent to the top surface 110 and extend downward. This portion 134 may be sloped (e.g., be a frustoconical surface angled downward from the outside inward).

Each flat facet 150 intersects the conical surface of the portion 134 along a curved edge 156. In detail, facet 150 is higher at adjoining edge 152 than at the lateral center, i.e., equidistant from opposing edge 152. That is, curved edge 156 slopes downwardly away from each edge 152, with the lowest point being equidistant from the opposing edge 152 of facet 150. Assuming that surface 134 is frustoconical and facet 150 is vertical, each curved edge 146 will define a hyperbola.

Returning to fig. 1, the inner surface 130 of the retaining ring 100 in combination with the lower surface of the flexible membrane 54 defines the substrate receiving recess 90. The retaining ring 100 prevents the substrate 10 from coming off the substrate receiving groove 90.

Generally, the substrate is circular and has a diameter of about 200mm to about 300 mm. The size of the groove 90 in top or bottom plan view is generally larger than the surface area of the substrate 10 to enable the substrate 10 to move in position relative to the retaining ring 100. For purposes of discussion, the Inner Radius (IR) of the retaining ring 100 is defined in a plan view of the retaining ring as the distance between the center C of the retaining ring 100 to the midpoint of the facet 150, which is equidistant between the two opposing edges 152. The inner diameter (twice the inner radius IR) is slightly larger (e.g., about 1 to 5mm larger) than the substrate radius. For example, for a 300mm diameter substrate, the retaining ring may have an inner diameter of about 301mm to 305 mm.

During the polishing process, carrier head 50, including retaining ring 100, is moved relative to polishing pad 60. The friction of the polishing pad 60 against the substrate 10 forces the substrate 10 against the inner surface 130 of the retaining ring 100. Due to the faceted structure, the substrate 10 contacts at least two facets 150 of the inner surface 130 for at least some periods of time.

However, since the radius of the substrate 10 is smaller than the radius of the inner surface 130 of the retaining ring 100, the substrate 10 and the inner surface 130 have different angular velocities. As a result, the pair (or tuple, etc.) of facets 150 that contacts the substrate 10 will shift over time. In other words, the retainer ring 100 rotates relative to the substrate 10.

Wear of the inner surface 130 of the retaining ring 100 may be reduced or more evenly distributed around the retaining ring as compared to a retaining ring having a cylindrical inner surface that contacts the substrate 10. Without being bound to any particular theory, when the inner surface of the retaining ring is cylindrical, the substrate having a circular outer periphery contacts the inner surface at a single location. In contrast, multiple contacts may allow the force of the substrate 10 against the inner surface 130 to be more widely distributed, thereby reducing the overall force at any particular point and reducing wear. The reduced wear may allow the retaining ring to have an increased life expectancy.

Again, without being bound to any particular theory, during relative motion between the retaining ring 100 and the substrate 10, the substrate does not make direct point-to-point contact with either the channels 122 or the channel openings at the edge 152 between the facets 150. In general, the channels 122 may create high stress areas in the retaining ring 100 where the retaining ring tends to be more susceptible to damage or fracture than other portions of the ring. By eliminating direct point-to-point contact between the channel 122 and the substrate 10, direct impact of high stress areas on the substrate 10 may be avoided and the likelihood of damage to the retaining ring may be reduced. As a result, wear of the retaining ring is reduced and the retaining ring can be used for a longer period of time.

In some polishing processes, relative motion between the substrate 10 and the retaining ring 100 can reduce asymmetry in the polished substrate and improve within-wafer uniformity. In the polishing substrate having asymmetry, the polishing substrate has a thickness variation with a change in angular coordinate. Again, without being bound to any particular theory, the multiple contacts between the substrate 10 and the retaining ring 100 may allow the substrate 10 to rotate relative to the carrier head 50, thereby angularly spreading the effect of any asymmetric pressure distribution from the carrier head 50 and thereby reducing the likelihood or amount of asymmetry, as compared to a single contact scenario.

The at least a lower portion 102 and the bottom surface 120 of the retaining ring 100 may be formed of a material that is chemically inert to the CMP process. The material should be sufficiently resilient so that contact of the substrate edge against the retaining ring 100 does not cause the substrate to chip or crack. However, the material should not be so resilient as to press the material into the substrate receiving groove when the carrier head applies downward pressure to the retaining ring 100. The material of the lower portion 102 should also be durable and have a low wear rate, but it is acceptable for the lower portion 102 of the retaining ring 100 to wear away.

For example, the lower portion 102 of the retaining ring 100 may be made of a plastic that is chemically inert during the CMP process. The plastic may have a durometer measurement on the shore D scale of about 80-95. In general, the modulus of elasticity of the plastic may be at about 0.3 × 10⁶psi-1.0×10⁶In psi range. Suitable plastics may include (e.g., consist of): polyphenylene Sulfide (PPS), Polyaryletherketone (PAEK), Polyetheretherketone (PEEK), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), Polytetrafluoroethylene (PTFE), Polybenzimidazole (PBI), Polyetherimide (PEI), Polyetherketoneketone (PEKK), polybutyl naphthalate (PBN), polyvinyl chloride (PVC), polycarbonate, combinations or composites of one or more of these plastics (e.g., one or more of these plastics and fillers such as glass or carbon fibers). The advantage of polyphenolic sulfide (PPS) is that it is a reliable and commonly used material for retaining rings.

The upper portion 104 of the retaining ring 100 may be made of a material that is at least as rigid as the lower portion 102. In some embodiments, the upper portion 104 may be made of a more rigid material than the lower portion 102. For example, the upper portion 104 may be a metal (e.g., aluminum or stainless steel) or ceramic material, or a plastic that is more rigid than the plastic of the lower portion 102. In some embodiments, the upper portion 104 has approximately the same rigidity (e.g., within 2%) as the lower portion, but has lower qualities, e.g., a greater proportion of contaminants, internal defects (such as inclusions or voids), and is therefore less expensive.

An adhesive (e.g., epoxy) may be used to join the lower portion 102 to the upper portion 104. Alternatively or in combination, mechanical fasteners and/or dovetail joints may be used to join the lower portion 102 to the upper portion 104.

In some embodiments, the lowest point on the curved edge 156 between the facet 150 and the conical portion 134 of the inner surface may be aligned with (i.e., at the same height as) the boundary between the upper ring 104 and the lower ring 102. However, in some embodiments, the lowest point on the curved edge 156 is above the boundary between the upper ring 104 and the lower ring 102.

To manufacture the retaining ring, the upper ring 104 may be formed from the frustoconical inner surface 134, while the lower ring 102 may be formed from a vertical cylindrical surface. The lower ring 102 is joined to the upper part 104. The inner surface 130 is then machined to form the facet 150. The upper ring 104 and the lower ring 102 may be formed by machining a suitable block of material or by injection molding.

The retaining ring 100 may also have other features or features in place of those discussed above. In some embodiments, the retaining ring 100 has one or more through holes extending horizontally or at a small angle to the horizontal through the body of the retaining ring from the inner surface to the outer surface to allow fluid (e.g., gas or liquid) to pass from the interior to the exterior, or from the exterior to the interior, of the retaining ring during polishing. The through holes may be evenly spaced around the retaining ring.

In some embodiments, one or more surfaces of the retaining ring (e.g., the inner surface 130 and/or the outer surface 140) may be coated with a film. The membrane may be a hydrophobic or hydrophilic membrane, and/or may act as a protective membrane. For example, the film may be Polytetrafluoroethylene (PTFE) or diamond-like carbon.

The inner surface of the retaining ring may have other geometries than the flat-faceted regular polygon described with reference to fig. 1-7. For example, referring to fig. 8-12, the inner surface 130 of the retaining ring may have a plurality of inwardly extending protrusions 200. The protrusion may extend inwardly from a circle having a first radius R1 to a circle having a smaller second radius R2 (shown in fig. 8). Examples of the geometry of the inner surface 130 include zigzag, sawtooth, trapezoidal, and sinusoidal, but other geometries are possible. There may be seven to one hundred fifty projections spaced around the inner surface of the retaining ring. The projections may be spaced at equal angular intervals around the retaining ring. Alternatively, the spacing between the protrusions may vary (e.g., in a regular pattern).

For some embodiments, for example as shown in fig. 8 and 10, each tab may be joined at its edge to the immediately adjacent tab. For example, the area between each pair of adjacent projections may not include a flat or arcuate surface that is substantially tangent to a circle defined by the first radius R1. Fig. 8 shows the protrusions as triangular, but other geometries are possible, such as trapezoidal (shown in fig. 10), sinusoidal (shown in fig. 12), and semi-circular. In addition, the inner tip of each protrusion and/or the intersection area between each protrusion may be rounded.

For some embodiments, such as shown in fig. 9-11, the innermost portion of each protrusion 200 may be a flat surface 202 (e.g., a flat facet) at the inner second radius R2. For example, referring to fig. 9, the protrusions 200 form a saw tooth geometry having a flat surface 202 and a flat side surface 206. The flat or curved region 204 of the inner surface may separate each tab 200 at the outer first radius R1. For a saw tooth geometry, each planar surface 202 may intersect an adjacent planar side surface 206 at an angle of about 90 ° (e.g., at an angle of 85 ° -90 °).

Referring to fig. 10-11, the protrusion 200 is trapezoidal, having a flat surface 202 and a flat side surface 206. For the trapezoidal protrusion 200, the angle between the flat surface 202 and the flat side surface 206 may be 115-145. In fig. 10, the projections 200 are separated at the outer first radius R1 by a flat or curved region 204, whereas in fig. 11, each projection 200 is joined at its edge to the immediately adjacent projection without a flat or curved region 204.

Referring to fig. 12, the projections 200 may form an undulating surface, e.g., the bottom inner edge may form a serpentine path. Each protrusion may be generally sinusoidal. A potential advantage of this embodiment is that the absence of sharp corners between the projections reduces the likelihood of the slurry sticking and drying in the corners, thereby potentially reducing defects.

Referring to fig. 13, portions of the inner surface 130 may have different surface textures (e.g., different surface roughness), or surface kerfs in different directions (e.g., vertical versus horizontal kerfs), or surface kerfs having different depths. For example, the inner surface 130 may include an arcuate section 210, the arcuate section 210 having a different surface texture than the arcuate section 212. In some embodiments, the portions (e.g., arcuate segments) having different surface textures are arranged in a regular pattern (e.g., an alternating pattern, such as alternating between smooth and rough, or alternating between horizontal cuts and vertical cuts). There may be seven to one hundred fifty portions spaced around the inner surface of the retaining ring. The portions may be spaced at equal angular intervals around the retaining ring. Alternatively, the spacing of the portions may vary (e.g., in a regular pattern). Each portion may have the same arc length, but this is not required.

For example, the arced segment 212 may be rougher than the arced segment 210. For example, the arcuate section 212 may have an Ra roughness of 4 to 2000 microinches (e.g., 8 to 64 microinches), while the arcuate section 210 may have an Ra roughness as low as about 2 microinches.

As another example, referring to FIG. 14, the arcuate section 212 may have a cut in a different direction than the arcuate section 210. The cutback direction of the arcuate section 212 may be perpendicular to the cutback direction of the arcuate section 210, but other angles (e.g., 20 ° to 90 °) are possible. In some embodiments, for example as shown in fig. 14, the arcuate sections 210, 212 alternate between horizontal cuts and vertical cuts. However, other directions are possible, such as alternating between a slanted left diagonal and a slanted right diagonal. In addition, more complex patterns of three or more surface textures are possible.

The different surface textures described above may be applied to the facets 150 or protrusions 200 of the embodiments discussed above. Thus, different facets 150 and protrusions 200 may have different surface textures (e.g., different surface roughness), or surface kerfs in different directions. Again, in some embodiments, the facets or protrusions having different surface textures are arranged in a regular pattern (e.g., an alternating pattern, such as alternating between smooth textures and rough textures, or alternating between horizontal kerfs and vertical kerfs).

While in the various embodiments above, the portion 132 of the inner surface 130 adjacent to the bottom surface 120 is vertical (perpendicular to the polishing surface), this portion 132 of the inner surface 130 may be sloped (e.g., at an angle of up to 30 ° from vertical).

Additionally, referring to fig. 15, a portion 132 of the inner surface 130 adjacent to the bottom surface 120 may have a differently sloped portion. For example, the inner surface 130 may include a facet or arc-shaped section 220, the facet or arc-shaped section 220 having a different angle of inclination relative to a horizontal plane than the facet or arc-shaped section 222. In some embodiments, the portions (e.g., facets or arcuate segments) are arranged in a regular pattern (e.g., an alternating pattern). For example, as shown in FIG. 15, the facet or arc section 220 is inclined outwardly (from bottom to top) and the facet or arc section 222 is inclined inwardly (from bottom to top). However, other combinations are possible (e.g., vertical versus pitch, or small pitch versus large pitch). There may be seven to one hundred fifty portions spaced around the inner surface of the retaining ring. The portions may be spaced at equal angular intervals around the retaining ring, or the spacing of the portions may vary (e.g., in a regular pattern).

The different inclination angles of the surfaces described above may be applied to the facets 150 or protrusions 200 of the embodiments discussed above. Thus, different facets 150 and protrusions 200 may have different inclination angles. The variation of the tilt angle may also be combined with the variation of the surface texture.

Referring to fig. 16, the portion of the retaining ring having an inner surface 130 that contacts the substrate may be an insert 106, the insert 106 fitting into a groove in the ring 108, the ring 108 extending above and radially outward of the insert 106. If the inner surface 130 becomes damaged or worn during extended use, the insert 106 may be replaced with a new insert 106.

The retaining ring may be formed from two or more stacked regions of different materials, or may be a single unitary ring (e.g., a solid plastic ring) of a homogeneous composition. The trenches, if present, may be aligned to regular points on the feature, or different trenches may intersect different points on the feature. The channel (if present) may cover anywhere from 5% to 90% of the bottom surface of the retaining ring. The outer surface of the retaining ring may include a step or lip, or be a single vertical cylindrical surface or a frustoconical surface. These concepts are applicable to retaining rings of different sizes (e.g., retaining rings for substrates 4 to 18 inches in diameter or larger).

Numerous embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other implementations are within the scope of the following claims.