Correcting Wafer Edge Asymmetry Using Polishing Pad Grooves

Abstract

To provide a chemical mechanical polishing system for reducing non-uniformity of polishing rate of an entire substrate.SOLUTION: A chemical mechanical polishing system includes a platen for holding a polishing pad, a carrier head for holding a substrate against a polishing surface of the polishing pad, and a controller. The polishing pad has a polishing control groove. The carrier is laterally movable by a first actuator across the polishing pad and rotatable by a second actuator. The controller synchronizes lateral oscillation of the carrier head with rotation of the carrier head such that over a plurality of successive oscillations of the carrier head, when a first angular swath of an edge portion of the substrate is at an azimuthal angular position about an axis of rotation of the carrier head, the first angular swath overlies the polishing surface and when a second angular swath of the edge portion of the substrate is at the azimuthal angular position, the second angular swath overlies the polishing control groove.SELECTED DRAWING: Figure 6A

Description

[Technical field]

[0001] The present disclosure relates to chemical mechanical polishing. [Background technology]

[0002] Integrated circuits are typically formed on substrates by sequentially depositing conductive, semiconducting, or insulating layers on silicon wafers. One fabrication step involves depositing a fill layer over a non-planar surface and planarizing the fill layer. In certain applications, the fill layer is planarized until the top surface of the patterned layer is exposed. For example, a conductive fill layer can be deposited over a patterned insulating layer to fill trenches or holes in the insulating layer. 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. In other applications, such as oxide polishing, the fill layer is planarized until a predetermined thickness remains on the non-planar surface. In addition, planarization of the substrate surface is typically required for photolithography.

[0003] Chemical mechanical polishing (CMP) is one commonly accepted method of planarization. This planarization method typically requires the substrate to 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 provides a controllable load to the substrate to press it against the polishing pad. An abrasive slurry is typically supplied to the surface of the polishing pad.

[0004] One problem in polishing is non-uniformity of the polishing rate across a substrate, for example, the edge of the substrate may be polished at a greater rate than the center of the substrate. Summary of the Invention

[0005] In one aspect, a chemical mechanical polishing system includes a rotatable platen for holding a polishing pad, a rotatable carrier head for holding a substrate against a polishing surface of the polishing pad during a polishing process, and a controller. The platen is rotatable by a motor, and the polishing pad has polishing control grooves concentric with an axis of rotation of the polishing pad. The carrier is moveable laterally across the polishing pad by a first actuator and rotatable by a second actuator. The controller is configured to control the first actuator and the second actuator to synchronize lateral oscillations of the carrier head with rotation of the carrier head over multiple successive oscillations of the carrier head such that when a first angular swath of an edge portion of the substrate is at an azimuthal position about the axis of rotation of the carrier head, the first angular swath is above the polishing surface, and when a second angular swath of the edge portion of the substrate is at the azimuthal position, the second angular swath is above the polishing control groove.

[0006] Implementations may include one or more of the following features.

[0007] The polishing pad may have a slurry supply groove, which may be narrower than the polishing control groove. The polishing pad may have a single polishing control groove surrounding the slurry supply groove, a single polishing control groove surrounded by the slurry supply groove, or exactly two polishing control grooves with the slurry supply groove disposed between the two polishing control grooves. The controller may be configured to control the first actuator and the second actuator such that a first frequency of rotation of the carrier head is equal to an integer multiple of a second frequency of lateral vibration of the carrier head.

[0008] In another aspect, a chemical mechanical polishing system includes a rotatable platen for holding a polishing pad, a rotatable carrier head for holding a substrate against a polishing surface of the polishing pad during a polishing process, and a controller. The platen is rotatable by a motor, and the polishing pad has a polishing control groove concentric with an axis of rotation of the polishing pad, the polishing groove having a plurality of arcuate segments. The carrier head is rotatable by an actuator. The controller is configured to control the motor and the actuator to synchronize a rotation of the platen with a rotation of the carrier head such that, over a plurality of successive rotations of the carrier head, when a first angular swath of an edge portion of the substrate is at an azimuthal position about the axis of rotation of the carrier head, a second angular swath is over an area of ​​the polishing surface between the arcuate segments, and when a second angular swath of the edge portion of the substrate is at the azimuthal position, the second angular swath is over an arcuate segment of the polishing control groove.

[0009] Implementations may include one or more of the following features.

[0010] The arcuate segments can be equiangularly spaced about an axis of rotation of the platen. The arcuate segments can have equal lengths. Each arcuate segment can subtend an arc of 10 to 45 degrees. There are 4 to 20 arcuate segments. The polishing pad can further include a slurry supply groove, and the slurry supply groove can be narrower than the polishing control groove. The controller is configured to control the motor and actuators such that a first frequency of rotation of the carrier head is an integer multiple of a second frequency of rotation of the platen.

[0011] The improvements may include, but are not limited to, one or more of the following: Non-uniformity, particularly angularly asymmetric non-uniformity near the edge of the substrate, may be reduced.

[0012] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will become apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view of a chemical mechanical polishing system including a polishing pad having polishing control grooves. [Diagram 2] FIG. 1 is a schematic cross-sectional view of a radial section of a polishing pad having both slurry supply grooves and polishing control grooves. [Figure 3A] 2A-2C are schematic top views of an example chemical mechanical polishing apparatus illustrating a carrier head in different lateral positions. [Figure 3B] 2A-2C are schematic top views of an example chemical mechanical polishing apparatus illustrating a carrier head in different lateral positions. [Figure 4] 1 is an exemplary graph of substrate position on a platen versus time. [Figure 5A] 1A-1D are schematic top views of a chemical mechanical polishing apparatus showing a carrier head in different lateral positions. [Figure 5B] 1A-1D are schematic top views of a chemical mechanical polishing apparatus showing a carrier head in different lateral positions. [Figure 6A] 3A-3C are schematic top views of another embodiment of a chemical mechanical polishing apparatus showing a carrier head in different lateral positions. [Figure 6B] 3A-3C are schematic top views of another embodiment of a chemical mechanical polishing apparatus showing a carrier head in different lateral positions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Like reference numbers and designations in the various drawings indicate like elements.

[0015] In chemical mechanical polishing, the removal rate at the edge of the substrate may be different from the removal rate at the center of the substrate. Furthermore, the polishing rate near the edge of the substrate need not be uniform along the circumference. This effect can be referred to as "edge asymmetry." To address the resulting substrate thickness irregularities, the substrate can be transferred to a dedicated polishing "touch-up" tool to polish localized areas on the substrate. Such tools can be used to correct the substrate edge asymmetry. For example, after the polishing process is completed, thicker areas at the edge of the substrate can be locally polished to provide a substrate of uniform thickness. However, such touch-up tools have a low throughput and touch-up tools add additional cost and footprint to a manufacturing facility.

[0016] One approach that can address this issue is to synchronize the rotation of the carrier head with the lateral movement of the carrier head or the rotation of the platen to preferentially place the over-polished areas of the substrate on the polishing control grooves. This approach can reduce the non-uniformity of the polished substrate, particularly the edge asymmetry. Moreover, this approach can be applied to the chemical mechanical polishing tool itself, thus avoiding large capital expenses and the installation of new tools.

[0017] 1 shows an example of a polishing station of a chemical mechanical polishing system 20. The polishing system 20 includes a rotatable, disk-shaped platen 24 on which a polishing pad 30 is disposed. The platen 24 is operable to rotate about an axis 25. For example, a motor 26 can rotate a drive shaft 28 to rotate the platen 24. The polishing pad 30 can be a two-layer polishing pad with an outer polishing layer 32 and a softer backing layer 34. The outer polishing layer 32 has an abrasive surface 36.

[0018] The polishing system 20 may include a feed port or integrated feed rinse arm 92 for dispensing a polishing fluid 94, such as a polishing slurry, onto the polishing pad 30. The polishing system 20 may include a pad conditioner apparatus 40 with a conditioning disk 42 to maintain the surface roughness of the polishing surface 36 of the polishing pad 30. The conditioning disk 42 may be disposed on the end of an arm 44 that may swing to sweep the disk 42 radially across the polishing pad 30.

[0019] Carrier head 70 is operable to hold substrate 10 against polishing pad 30. Carrier head 70 is suspended from support structure 50, e.g., a carousel or track, and is connected to carrier head rotation motor 56 by drive shaft 58 such that the carrier head can rotate about axis 55. Carrier head 70 may be oscillated laterally, for example, on a slider on the carousel, by movement along the track, or by rotational oscillation of the carousel itself.

[0020] Carrier head 70 includes a housing 72, a substrate backing assembly 74 including a base 76 and a flexible membrane 78 that defines a number of pressurizable chambers 80, a gimbal mechanism 82 (which may be considered part of assembly 74), a loading chamber 84, a retaining ring assembly 100, and an actuator 122.

[0021] The housing 72 may be generally circular in shape and may be connected to the drive shaft 58 so as to rotate therewith during polishing. There may be a passage (not shown) extending through the housing 72 for pneumatic control of the carrier head 100. The substrate backing assembly 74 is a vertically movable assembly disposed below the housing 72. A gimbal mechanism 82 allows the base 76 to be gimbaled relative to the housing 72 while preventing the base 76 from moving laterally relative to the housing 72. A loading chamber 84 is disposed between the housing 72 and the base 76 to apply a load, i.e., downward pressure or weight, to the base 76 and thus to the substrate backing assembly. The vertical position of the substrate backing assembly 74 relative to the polishing pad is also controlled by the loading chamber 84. The underside of the flexible membrane 78 provides a mounting surface for the substrate 10.

[0022] In some implementations, the substrate backing assembly 74 is not a separate component that is moveable relative to the housing 72. In this case, the chamber 84 and gimbal 82 are not required.

[0023] 1 , the polishing pad 30 has at least one polishing control groove 102 formed in the polishing surface 36. Each polishing control groove 102 is a recessed area of ​​the polishing pad 30. Each polishing control groove 102 may be an annular groove, e.g., a circular groove, and may be concentric with the axis of rotation 25 of the platen 24. Each polishing control groove 102 provides an area of ​​the polishing pad 30 that does not contribute to polishing.

[0024] The walls of the abrasive control groove 102 are perpendicular to the abrasive surface 36. The abrasive control groove 102 can have a rectangular or U-shaped cross section. The abrasive control groove 102 can be 10 to 80 mils deep, for example, 10 to 60 mils deep.

[0025] In some embodiments, the pad 30 includes polishing control grooves 102a located near the outer edge of the polishing pad 30, e.g., within 15%, e.g., within 10%, e.g., within 5% (in radius) of the outer edge. For example, the grooves 102 may be located a radial distance of 14 inches from the center of a platen having a diameter of 30 inches.

[0026] In some embodiments, the pad 30 includes polishing control grooves 102b located near the center of the polishing pad 30, e.g., within 15%, e.g., within 10% (in radius) of the center or axis of rotation 25. For example, grooves 102b may be located at a radial distance of 1 inch from the center of a platen having a diameter of 30 inches.

[0027] In some embodiments, the pad 30 includes only polishing control grooves 102a located near the outer edge of the polishing pad 30 (see FIGS. 3A and 3B). In this case, there may be only one polishing control groove 102a near the outer edge of the polishing pad 30. In some embodiments, the pad 30 includes only polishing control grooves 102b located near the center of the polishing pad 30. In this case, there may be only one polishing control groove 102b near the center of the polishing pad 30. In some embodiments, the pad 30 includes a first polishing control groove 102a located near the edge of the polishing pad 30 and a second polishing control groove 102b located near the center of the polishing pad 30 (see FIG. 1). In this case, there may be exactly two polishing grooves 102 in the polishing surface.

[0028] The polishing control groove 102 is sufficiently wide such that by placing a portion of the substrate 10 over the groove, the polishing rate at that portion is substantially reduced. In particular, for edge compensation, the groove 102 is sufficiently wide such that an annular band at the edge of the substrate, e.g., a band at least 3 mm wide, e.g., a band 3-15 mm wide, e.g., a band 3-10 mm wide, reduces the polishing rate. The polishing control groove 102 can be 5 to 50 millimeters wide, e.g., 10 to 20 millimeters wide.

[0029] When the substrate 10 is disposed on the polishing surface 36 of the polishing pad 30, the polishing surface 36 contacts and polishes the substrate 10 such that material removal occurs. On the other hand, when the edge of the substrate 10 is disposed over the polishing control grooves 102, there is no contact or polishing of the edge of the substrate 10 such that removal occurs. Optionally, the grooves 102 can provide a conduit for the passage of a polishing slurry without abrading the substrate 10.

[0030] 2, the polishing pad 30 may also include one or more slurry feed grooves 112. The slurry feed grooves 112 may be annular grooves, e.g., circular grooves, and may be concentric with the polishing control grooves 102. Alternatively, the slurry feed grooves may have another pattern, e.g., rectangular crosshatch, triangular crosshatch, etc. The slurry feed grooves may have a width of between about 0.015 and 0.04 inches (between 0.381 and 1.016 mm), e.g., 0.20 inches, and a pitch of between about 0.09 and 0.24 inches, e.g., 0.12 inches.

[0031] The slurry supply grooves 112 are narrower than the polishing control grooves 102. For example, the slurry supply grooves 112 can be narrower in width by at least a factor of three, such as at least a factor of six, such as between 6 and 100. The slurry supply grooves 112 can be uniformly spaced across the polishing pad 30. The polishing control grooves 102 can have a depth that is shallower, similar, or deeper than the slurry supply grooves 112. In some embodiments, the polishing control grooves 102 are the only grooves on the polishing pad that are wider than the slurry supply grooves 112. In some embodiments, the polishing control grooves 102a and 102b are the only grooves on the polishing pad that are wider than the slurry supply grooves 112.

[0032] 3A , during at least a portion of the polishing operation, e.g., a first duration, the substrate 10 can be positioned in a first position or a first range of positions such that a central portion 12 of the substrate 10 and an edge portion 14 of the substrate 10 are both polished by the polishing surface 36 of the polishing pad 30. Thus, no part of the substrate 10 overlaps the polishing control grooves 102. Although portions of the substrate 10 overlap the slurry supply grooves 112, the slurry supply grooves 112 are relatively closely spaced such that relative motion averages out the effect on the polishing rate.

[0033] 3B, during at least a portion of the polishing operation, e.g., a second duration, the substrate 10 can be positioned such that the central portion 12 of the substrate 10 is polished by the polishing surface 36 and the region 14a of the edge portion 14 of the substrate 10 is above the polishing control grooves 102. During the second duration, the substrate 10 can be held laterally fixed in the second position. Thus, the central portion 12 of the substrate 10 is polished during the second duration, while the region 14a of the edge portion 14 of the substrate 10 located above the polishing control grooves 102 is not polished. Because a portion of the edge portion 14 (shown as 14b) remains above the polishing surface 36, the edge portion 14 is still polished to some extent, but at a lower rate than the central portion 12 due to the lack of polishing in the region 14a. Although a portion of the substrate 10 overlaps the slurry supply grooves 112, the slurry supply grooves 112 are relatively closely spaced, allowing the relative motion to average out the effect on the polishing rate.

[0034] The particular time that region 14a of edge portion 14 remains over polishing-control groove 102 depends on the frequency and magnitude of the vibration and the dimensions of the groove and substrate. A controller 90 (see FIG. 1 ) can control motors 25, 56 to control the rotational speed of platen 20 and carrier head 70, and can control actuators coupled to the support to control the frequency and magnitude of the lateral vibration of carrier head 70.

[0035] 4, the substrate may be moved in an oscillatory pattern in which the substrate performs a single sweep for a first duration T1 (t0-t1). In some embodiments, at the end of the first duration, the substrate is held in a position where the central portion 12 of the substrate 10 is positioned over the polishing area of ​​the polishing pad 30 and the edge portion 14 of the substrate 10 is positioned and held over the polishing control grooves 102 for a second duration T2 (t1-t2). In this case, the frequency of the oscillation is 1 / (T1+T2).

[0036] The ratio of the first duration T1 to the second duration T2 can be selected to reduce the polishing rate of the edge portion 14 by a desired amount compared to the central portion 12. For example, the ratio T1 / T2 can be selected to achieve a desired average polishing rate at the edge, e.g., to achieve the same average polishing rate as the central portion 12.

[0037] 5A, as described above, the substrate may have asymmetry. For example, the edge portion 14 of the substrate 10 may have a first angular swath 16a and a second angular swath 16b, each having a different thickness. To compensate for the edge asymmetry of the substrate 10, the controller 90 may cause the movement of the carrier head 70 such that the different swaths of the edge portion 14 of the substrate 10 are either above the polishing control groove 102 or above the polishing area of ​​the polishing pad 30. This may be done by synchronizing the vibration of the carrier head 70 with the rotation of the carrier head 70. For example, each second duration T2 corresponds to the time that the second angular swath 16b is above the polishing control groove 102.

[0038] For example, assuming that the first angular swath 16a is thicker than the second angular swath 16b, the lateral position of the carrier head and the rotation of the carrier head can be synchronized to position the carrier head 70 such that when the first angular swath 16a of the substrate 10 is at a given azimuthal position 18 about the axis of rotation 55 of the carrier head 70, the first angular swath 16a is over the polishing portion 104 of the polishing pad 30. The azimuthal position 18 can be the position on the carrier head 70 furthest from the axis of rotation 25 of the polishing pad. Similarly, the azimuthal position 18 can be on a line passing through the axis of rotation 25 of the polishing pad 30 and the axis of rotation 55 of the carrier head 70.

[0039] 5B, as the carrier head 70 rotates, the second angular swath 16b moves toward the predetermined azimuthal position 18. The lateral position of the carrier head 70 and the rotation of the carrier head 70 can be synchronized such that the carrier head 70 moves laterally such that the second angular swath 16b is above the polishing control groove 102 by the time the second angular swath 16b is at the predetermined azimuthal position 12 about the rotation axis 55 of the carrier head 70. As a result, the first angular swath 16a is polished at a higher rate than the second angular swath 16b. This can provide a more uniform substrate 10, particularly reducing edge asymmetry.

[0040] To achieve synchronization, the controller 90 may be configured to control the motors 26 and actuators 58 such that a first frequency of rotation of the carrier head is equal to an integer multiple of a second frequency of lateral vibration of the carrier head. For example, the first frequency of rotation may be equal to the second frequency. Note that this synchronization must be maintained fairly accurately. Mismatch will result in precession of the angular swath for a given azimuthal position 18, thus negating the effectiveness of edge asymmetry correction.

[0041] 4 shows the substrate being held in place for a second duration T2, this is not required. Even if the carrier head 70 is constantly sweeping back and forth across the polishing pad 30 (e.g., the radial position is a trigonometric or sinusoidal function of time), there can be a period of time during which the second angular swath 16b is above the polishing control groove 102.

[0042] Additionally, while the above discussion has focused on a polishing pad having a single polishing control groove 102a near the periphery of the polishing pad, similar principles can also be applied when a polishing groove 120b is located near the center of the polishing pad such that a second angled swath 16b that would otherwise be over-polished is positioned over the polishing control groove 102b to reduce the polishing rate of that swath.

[0043] 6A and 6B, in some embodiments, the grinding control groove 102 may include a plurality of arcuate segments 132 (rather than being a continuous circle). There may be between 4 and 20 arcuate segments 132. The arcuate segments 132 may be equiangularly spaced about the platen's axis of rotation 25. The arcuate segments 132 may have equal lengths. Each arcuate segment may subtend an arc of between 15 and 90 degrees.

[0044] The controller 90 can synchronize the rotation of the carrier head 70 with the rotation of the platen 24 and polishing pad 30 (indicated by arrow C) to reduce the polishing rate in the over-polished areas of the substrate. In this configuration, no lateral sweep of the carrier head 70 is required to achieve edge asymmetry compensation.

[0045] For example, if the first angular swath 16a of the edge portion 14 of the substrate 10 is thicker than the second angular swath 16b, polishing can begin with the first angular swath 16a overlying a section 130 of the polishing surface 36 between the arcuate segments 132 of the groove. As both the polishing pad 30 and the carrier head 70 rotate, the second angular swath 16b moves outward toward the radius at which the arcuate segments are located. The controller 90 can synchronize the rotation of the carrier head 70 and the rotation of the polishing pad 30 such that when the second angular swath 16b reaches the radial position of the groove 102, the second angular swath 16b is over one of the arcuate segments 132. As a result, the first angular swath 16a can be polished at a higher rate than the second angular swath 16b, thereby reducing edge asymmetry and improving uniformity.

[0046] To achieve synchronization, the controller 90 may be configured to control the motors 26, 56 such that a first frequency of rotation of the carrier head is equal to an integer multiple of a second frequency of rotation of the platen. For example, the first frequency of rotation may be equal to N, where N is a submultiple of the number of arc segments 132. In some implementations, N is equal to 1. Note that this synchronization must be maintained fairly accurately. Mismatch will result in precession of the angular swath for a given azimuthal position 18, thus negating the effectiveness of edge asymmetry correction.

[0047] As used herein, the term substrate can include, for example, a production substrate (e.g., including multiple memory or processor dies), a test substrate, a bare substrate, and a gating substrate. The substrate can be at various stages of integrated circuit fabrication, for example, the substrate can be a bare wafer or can include one or more deposited and / or patterned layers. The term substrate can include a circular disk or a rectangular sheet.

[0048] The controller 90 may include a dedicated microprocessor, such as an ASIC, or a conventional computer system executing a computer program stored on a non-volatile computer readable medium. The controller 90 may include a central processing unit (CPU) and memory containing associated control software.

[0049] The above polishing system and method can be applied to various polishing systems. Either the polishing pad, the carrier head, or both can move to provide relative motion between the polishing surface and the substrate. The polishing pad can be a circular (or other shaped) pad fixed to a platen. The polishing layer can be a standard (e.g., polyurethane with or without filler), soft, or fixed abrasive. Although relative positional terms are used, it should be understood that the polishing surface and the substrate can be held in a vertical or other orientation.

[0050] Although specific embodiments of the invention have been described, other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results.

Claims

1. a platen rotatable about a first axis of rotation by a motor and configured to hold a polishing pad, the polishing pad having a polishing surface and a polishing control groove concentric with the axis of rotation of the platen; a rotatable carrier head for holding a substrate against the polishing surface of the polishing pad during a polishing process, the carrier head being movable laterally across the polishing pad by a first actuator and rotatable about a second axis of rotation by a second actuator; a controller configured to control the first actuator and the second actuator to synchronize lateral oscillations of the carrier head with rotation of the carrier head such that, over multiple successive oscillations of the carrier head, when a first angular swath of the annular edge portion of the substrate is at an azimuthal position about the second rotation axis of the carrier head, the first angular swath is above the polishing surface, and when a second angular swath of the annular edge portion of the substrate, which is over-polished during the polishing process compared to the first angular swath, is at the azimuthal position, the second angular swath is above the polishing control groove; A chemical mechanical polishing system comprising:

2. The system of claim 1 , wherein the polishing pad further comprises a slurry supply groove.

3. The system of claim 2 , wherein the slurry supply groove is narrower than the polishing control groove.

4. The system of claim 3 , wherein the polishing pad has a single polishing control groove surrounding the slurry supply groove.

5. The system of claim 3 , wherein the polishing pad has a single polishing control groove surrounded by the slurry supply groove.

6. 4. The system of claim 3, wherein the polishing pad has exactly two polishing control grooves, and the slurry supply groove is disposed between the two polishing control grooves.

7. 2. The system of claim 1, wherein the controller is configured to control the first actuator and the second actuator such that a first frequency of rotation of the carrier head is equal to an integer multiple of a second frequency of lateral vibration of the carrier head.

8. a platen rotatable by a motor about a first axis of rotation and configured to hold a polishing pad, the polishing pad having a polishing surface and a polishing control groove concentric with the first axis of rotation, the polishing control groove having a plurality of arcuate segments; a rotatable carrier head for holding a substrate against the polishing surface of the polishing pad during a polishing process, the carrier head being rotatable about a second axis of rotation by an actuator; a controller configured to control the motors and the actuators to synchronize a rotation of the platen with a rotation of the carrier head over multiple successive rotations of the carrier head such that, when a first angular swath of the annular edge portion of the substrate is at an azimuthal position about the second axis of rotation of the carrier head, the first angular swath is over an area of ​​the polishing surface between arcuate segments, and, when a second angular swath of the annular edge portion of the substrate that has been over-polished during the polishing process more than the first angular swath is at the azimuthal position, the second angular swath is over an arcuate segment of the polishing control groove; A chemical mechanical polishing system comprising:

9. The system of claim 8 , wherein the arcuate segments are equiangularly spaced about the axis of rotation of the platen.

10. The system of claim 8 , wherein the arcuate segments have equal lengths.

11. The system of claim 8 , wherein each arcuate segment subtends an arc of between 5 and 15 degrees.

12. The system of claim 8, wherein there are between 4 and 20 arc segments.

13. The system of claim 8 , wherein the polishing pad further comprises a slurry supply groove.

14. The system of claim 13 , wherein the slurry supply grooves are narrower than the polishing control grooves.

15. The system of claim 8 , wherein the controller is configured to control the motor and the actuator such that a first frequency of rotation of the carrier head is an integer multiple of a second frequency of rotation of the platen.

16. 1. A method for chemical mechanical polishing, comprising: Rotating the polishing pad about a first axis of rotation; placing a substrate against the polishing pad having a polishing surface and a polishing control groove concentric with the first axis of rotation; rotating the substrate about a second axis of rotation; oscillating the substrate laterally across the polishing pad and rotating the substrate such that, over a plurality of successive oscillations of the substrate, a first angular swath of the annular edge portion of the substrate is above the polishing surface when the first angular swath is at an azimuthal position about the second axis of rotation, and a second angular swath of the annular edge portion of the substrate, which is over-polished during the polishing process compared to the first angular swath, is above the polishing control groove when the second angular swath is at the azimuthal position; The method includes:

17. The method of claim 16 , wherein a first frequency of rotation of the substrate is equal to an integer multiple of a second frequency of lateral vibration of the substrate.

18. 1. A method for chemical mechanical polishing, comprising: Rotating the polishing pad about a first axis of rotation; placing a substrate against the polishing pad having a polishing surface and a polishing control groove concentric with the first axis of rotation, the polishing control groove having a plurality of arcuate segments; rotating the substrate about a second axis of rotation such that, over a plurality of successive rotations of the substrate, a first angular swath of the annular edge portion of the substrate is at an azimuthal position about the second axis of rotation, the first angular swath is on an area between the arcuate segments of the polishing surface, and a second angular swath of the annular edge portion of the substrate, which is over-polished during the polishing process more than the first angular swath, is at the azimuthal position, the second angular swath is on an arcuate segment of the polishing control groove; The method includes:

19. 20. The method of claim 18, wherein the first frequency of rotation of the substrate is equal to an integer multiple of a second frequency of rotation of the polishing pad.

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