Grooves for edge and hot spot compensation in chemical mechanical polishing

Abstract

A method for chemical mechanical polishing includes rotating a polishing pad about a rotation axis, positioning a substrate against the polishing pad, dispensing polishing liquid onto the polishing pad, and laterally oscillating the substrate across the polishing pad. The polishing pad has polishing rate adjustment grooves concentric with the rotation axis, and a coolant, diluent, or both are dispensed into the polishing rate adjustment grooves such that the polishing rate decreases in an annular region of the polishing pad positioned radially inward from the polishing rate adjustment grooves. The annular region surrounds a central region of the polishing pad, wherein the polishing rate is substantially unaffected by the coolant, diluent, or both.

Description

Grooves for edge and hot spot compensation in chemical mechanical polishing The present disclosure relates to chemical mechanical polishing of substrates. Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconductive, or insulating layers on a silicon wafer. One manufacturing step involves depositing a filler layer over a non-planar surface and planarizing the filler layer. For some applications, the filler layer is planarized until the top surface of the patterned layer is exposed. For example, a conductive filler layer can be deposited over a patterned insulating layer to fill grooves 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. For other applications, such as oxide polishing, the filler layer is planarized until a predetermined thickness remains over the non-planar surface. In addition, photolithography typically requires planarization of the substrate surface. Chemical mechanical polishing (CMP) is a well-established planarization method. This process typically requires mounting a substrate on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head applies a controllable load to the substrate, pushing it against the polishing pad. An abrasive polishing slurry is typically applied to the surface of the polishing pad. One problem in polishing is the non-uniformity of the polishing rate across the substrate. For example, the edge portion of the substrate may be polished at a higher rate relative to the center portion of the substrate. In one aspect, a method for chemical mechanical polishing includes rotating a polishing pad about a rotational axis; positioning a substrate against the polishing pad; dispensing a polishing liquid onto the polishing pad; and dispensing a coolant, a diluent, or both into a polishing rate adjustment groove concentric with the rotational axis such that the polishing rate is reduced in an annular region of the polishing pad located radially inward from the polishing rate adjustment groove. The annular region surrounds a central region of the polishing pad, wherein the polishing rate is substantially unaffected by the coolant, the diluent, or both. The substrate is laterally oscillated across the polishing pad such that, for a first duration, a central portion and an edge portion of the substrate are positioned above the central region of the polishing pad, such that the central portion and the edge portion of the substrate are polished by the central region of the polishing pad for the first duration, and, for a second duration, a central portion of a held substrate is positioned above the central region of the polishing pad and an angularly extending segment of the edge portion of the substrate is positioned above the annular region, such that the central portion of the substrate is polished by the central region of the polishing pad for a second duration and the edge portion of the substrate is polished by both the central region and the annular region of the polishing pad for the second duration, thereby reducing the polishing rate of the edge portion. In another aspect, a polishing system includes: a rotatable platform for supporting a polishing pad, the polishing pad having a polishing rate adjustment groove concentric with the rotation axis of the platform; a first dispenser for delivering a polishing liquid onto the polishing pad; a second dispenser for delivering a coolant, a diluent, or both into the polishing rate adjustment groove such that the polishing rate is reduced in an annular region of the polishing pad positioned radially inward from the polishing rate adjustment groove, wherein the annular region surrounds a central region of the polishing pad, wherein the polishing rate is substantially unaffected by the coolant, the diluent, or both; a carrier head for holding a substrate against the polishing pad, the carrier head being movable laterally across the polishing pad; an actuator for moving the carrier head; and a controller coupled to the actuator. The controller is configured to cause the actuator to oscillate the carrier head and the substrate laterally across the polishing pad so as to cause the actuator to position a center portion of the substrate and an edge portion of the substrate above a center region of the polishing pad for a first duration so that the center portion of the substrate and the edge portion of the substrate are polished by the center region of the polishing pad for the first duration, and to cause the actuator to position the center portion of the substrate above the center region of the polishing pad and to position an angularly extended segment of the edge portion of the substrate above the annular region for a second duration so that the center portion of the substrate is polished by the center region of the polishing pad for a second duration and the edge portion of the substrate is polished by both the center region and the annular region of the polishing pad for the second duration so as to reduce the polishing rate of the edge portion. In another aspect, a method for chemical mechanical polishing includes rotating a polishing pad about a rotational axis; positioning a substrate against the polishing pad; dispensing a polishing liquid onto the polishing pad; and dispensing a coolant, a diluent, or both onto the polishing pad at a location radially inward from, but proximate to, a polishing rate adjustment groove concentric with the rotational axis such that the polishing rate is reduced in an annular region of the polishing pad positioned radially inward from the polishing rate adjustment groove. The annular region surrounds a central region of the polishing pad, wherein the polishing rate is substantially unaffected by the coolant, the diluent, or both. The polishing rate adjustment groove is wider than a slurry dispensing groove in the central portion of the polishing pad. The substrate is oscillated laterally across the polishing pad such that, for a first duration, a central portion of the substrate and an edge portion of the substrate are positioned over a central region of the polishing pad such that the central portion of the substrate and the edge portion of the substrate are polished by the central region of the polishing pad for the first duration, and, for a second duration, the central portion of the substrate is held positioned over the central region of the polishing pad and an angularly extending segment of the edge portion of the substrate is positioned over the annular region such that the central portion of the substrate is polished by the central region of the polishing pad for a second duration, and the edge portion of the substrate is polished by both the central region and the annular region of the polishing pad for the second duration so as to reduce a polishing rate of the edge portion. In another aspect, a polishing system includes: a rotatable platform for supporting a polishing pad having a polishing rate adjustment groove concentric with a rotational axis of the platform; a first dispenser for delivering a polishing liquid to the polishing pad; a second dispenser for delivering a coolant, a diluent, or both to the polishing pad at a position radially inward from but proximate to the polishing rate adjustment groove, such that the polishing rate is reduced in an annular region of the polishing pad positioned radially inward from the polishing rate adjustment groove, wherein the annular region surrounds a central region of the polishing pad, wherein the polishing rate is substantially unaffected by the coolant, the diluent, or both; a carrier head for holding a substrate against the polishing pad, the carrier head being movable laterally across the polishing pad; an actuator for moving the carrier head; and a controller coupled to the actuator. The controller is configured to cause the actuator to oscillate the carrier head and the substrate laterally across the polishing pad so as to cause the actuator to position a center portion of the substrate and an edge portion of the substrate above a center region of the polishing pad for a first duration so that the center portion of the substrate and the edge portion of the substrate are polished by the center region of the polishing pad for the first duration, and to cause the actuator to position the center portion of the substrate above the center region of the polishing pad and to position an angularly extended segment of the edge portion of the substrate above the annular region for a second duration so that the center portion of the substrate is polished by the center region of the polishing pad for a second duration and the edge portion of the substrate is polished by both the center region and the annular region of the polishing pad for the second duration so as to reduce the polishing rate of the edge portion. Embodiments may optionally include, but are not limited to, one or more of the following advantages. Radial polishing non-uniformities, such as those caused by different polishing rates at different portions of the substrate, can be controlled and corrected. For example, controlling the position of the substrate relative to areas of cooler polishing liquid, diluted polishing liquid, or a softer polishing pad can provide edge correction. Furthermore, because adjustments to the polishing can be performed within the polishing station rather than as part of a separate module, the impact on throughput is minimized. Polishing "hot spots," such as limited angular regions at the edge of the substrate that are over-polished, can be reduced. The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, as well as from the claims. As mentioned above, when a substrate is polished by a polishing pad, the edge of the substrate may be polished at a higher rate than the center of the substrate, resulting in an unevenly polished substrate. In addition, polishing "hot spots" may occur, such as limited angular regions at the edge of the substrate that are over-polished. However, several techniques can be used to reduce the polishing rate at the edge of the substrate and / or reduce polishing hot spots. These techniques can be used alone or in combination. In one aspect, a cold liquid or diluent can be dispensed into the polishing rate adjustment groove, and a substrate can be positioned with its edge adjacent the polishing rate adjustment groove. Old liquid or diluent can flow from the polishing rate adjustment groove below the edge portion of the substrate, thereby reducing the polishing rate at the edge of the substrate. In another aspect, the outer annular portion of the polishing pad can be replaced with a material that is softer and has a lower polishing rate than the polishing material in the central portion of the polishing pad. The substrate can be positioned with its edge over this annular region to reduce the polishing rate at the edge of the substrate. In yet another aspect, grooves can be placed on the polishing pad that preferentially direct polishing liquid away from an outer annular region of the polishing pad. The substrate can be positioned with its edge above this annular region to reduce the polishing rate at the edge of the substrate. In yet another aspect, a retaining ring having a high density of slurry distribution channels can be used for polishing substrates with high edge polishing rates. The slurry distribution channels can be configured to preferentially direct polishing liquid away from the substrate, which can reduce the polishing rate at the substrate edge. FIG1 illustrates an example of a polishing station of a chemical mechanical polishing system 20. Polishing system 20 includes a rotatable, disc-shaped platform 24 on which a polishing pad 30 is positioned. Platform 24 is operable to rotate about axis 25. For example, motor 26 can rotate drive shaft 28 to rotate platform 24. Polishing pad 30 can be a two-layer polishing pad having an outer polishing layer 32 and a softer backing layer 34. Outer polishing layer 32 has a polishing surface 36. A plurality of grooves 100 may be formed in the polishing surface 36. In some embodiments, the plurality of grooves 100 include both a plurality of polishing liquid distributing grooves 110 and polishing rate adjusting grooves 120. In some embodiments, the plurality of grooves 100 include only the polishing liquid distributing grooves 110. The polishing liquid distribution grooves 110 can be annular grooves, for example, circular grooves, and can be concentric with the center of the polishing pad 30, for example, with the rotation axis 25. Alternatively, the polishing liquid distribution grooves 110 can have another pattern, for example, rectangular cross-hatching, triangular cross-hatching, etc. The polishing liquid distribution grooves 110 can have a width between about 0.015 and 0.04 inches (between 0.381 and 1.016 mm), such as 0.20 inches, and a pitch between about 0.09 and 0.24 inches, such as 0.12 inches. The polishing liquid distribution grooves 110 can be evenly spaced across the polishing pad 30. The polishing system 20 can include a supply arm or combined supply-rinse arm 62 having a port 64 to dispense polishing liquid 66, such as an abrasive slurry, onto the polishing pad 30. The port 64 can be located near the rotation axis 25 so that centrifugal force carries the polishing liquid outward across the polishing surface 36. The polishing system 20 may include a pad conditioner apparatus 40 having 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 positioned at the end of an arm 44 that may swing to sweep the disk 42 radially across the polishing pad 30. Carrier head 70 is operable to hold substrate 10 against polishing pad 30. Carrier head 70 is suspended from a support structure 50 (e.g., a turntable or track) and is connected to a carrier head rotation motor 56 via a drive shaft 58 so that the carrier head can rotate about an axis 55. Optionally, carrier head 70 can oscillate laterally, for example, on a slide on a turntable, by moving along a track, or by rotational oscillation of the turntable itself. The carrier head 70 includes a housing 72, a flexible membrane 74 defining a plurality of pressurizable chambers 76a, 76b, 76c, and a retaining ring 80 secured to the housing 72. In operation, a bottom surface 82 of the retaining ring 80 contacts the polishing surface 36. Optionally, a plurality of channels may be formed in the bottom surface 82 of the retaining ring 80 to allow the polishing liquid 66 to flow between the interior and exterior of the retaining ring 80. The lower surface of the flexible membrane 78 provides a mounting surface for the substrate 10. The housing 72 may be generally circular in shape and may be connected to the drive shaft 58 for rotation therewith during polishing. A passageway (not shown) may extend through the housing 72 for pneumatic control of the carrier head 70. FIG1 , FIG2A , and FIG2B illustrate an embodiment in which the polishing pad 30 has at least one (e.g., exactly one) polishing rate adjustment groove 120 formed in the polishing surface 36 . The polishing rate adjustment groove 120 is a recessed area of ​​the polishing pad 30 . The polishing rate adjustment groove 120 can be an annular groove, e.g., circular, and can be concentric with the rotation axis 25 . The polishing rate adjustment groove 120 can surround the polishing liquid distribution groove 110 (for ease of illustration, the polishing liquid distribution groove 110 is not shown in FIG2A , but is shown in FIG2B ). Assuming the polishing liquid distribution groove 110 is a circular groove, the polishing rate adjustment groove 120 can be concentric with the polishing liquid distribution groove 110. In some embodiments, no additional polishing liquid distribution groove 110 is radially outward from the polishing rate adjustment groove 120 . The walls of the polishing rate adjustment groove 120 are perpendicular to the polishing surface 36. The bottom surface of the polishing rate adjustment groove 120 is parallel to the polishing surface 36, although in some embodiments, the bottom surface of the polishing rate adjustment groove 120 can be angled or U-shaped. The depth of the polishing rate adjustment groove 120 can be 10 to 80 mils, for example, 10 to 60 mils. The polishing rate adjustment groove 120 can have a width of three to fifty, for example, five to fifty, for example, three to ten, for example, ten to twenty millimeters. In some embodiments, the polishing rate adjustment groove 120 is located near the outer edge of the polishing pad 30, for example, within 15% of the outer edge, such as within 10% (in terms of radius). For example, the polishing rate adjustment groove 120 can be located at a radial distance of fourteen inches from the center of a platform having a diameter of thirty inches. The polishing liquid distribution groove 110 is narrower than the polishing rate adjustment groove 120. For example, the polishing liquid distribution groove 110 can be at least 3 times narrower, for example, at least 6 times, such as 6 to 10 times narrower. The polishing rate adjustment groove 120 can have a smaller, similar, or larger depth than the polishing liquid distribution groove 110. In some embodiments, the polishing rate adjustment groove 120 is the only groove on the polishing pad 30 that is wider than the polishing liquid distribution groove 110. Referring to FIG. 1 , in an embodiment including a polishing rate adjustment groove 120 , the polishing system 20 includes a dispenser 130 having an outlet 132 for delivering a liquid 134 (see FIG. 1 ) that acts as a coolant, a diluent, or both. Specifically, the outlet 132 can be positioned directly above the polishing rate adjustment groove 120 , such that the liquid 134 flows directly above the polishing rate adjustment groove 120 . Alternatively, the outlet 132 can be positioned such that the liquid 134 flows onto the polishing surface. For example, the outlet 132 can be positioned such that the liquid 134 is dispensed radially inward from the polishing rate adjustment groove 120 , but proximate to the polishing rate adjustment groove 120 (e.g., within 10 cm, such as within 5 cm). Assuming that the liquid 134 is a coolant, the liquid coolant can be the polishing liquid 66, but cooled to, for example, 0 to 5°C. Alternatively, the liquid coolant can be deionized (DI) water; in this case, the liquid acts as both a coolant and a diluent. In either case, the liquid coolant can be sprayed, for example, atomized, through a nozzle providing the outlet 132. Assuming that the liquid 134 is a diluent, the liquid diluent may be deionized (DI) water. In this case, the liquid diluent may be dispensed at room temperature (eg, 20 to 23° C.). Referring to FIG. 2A , dispensing coolant and / or diluent into the polishing rate adjustment groove 120 creates an annular region 122 radially inward from and immediately adjacent to the polishing rate adjustment groove 120 in which the polishing rate is substantially reduced (but not completely eliminated). The annular region 122 may have a width of 2 to 10 mm. Without being limited to any particular theory, some coolant and / or diluent liquid 134 may overflow the polishing rate adjustment groove 120, but centrifugal force may limit the coolant and / or diluent liquid 134 from diffusing inward from the polishing rate adjustment groove 120. Again without being limited to any particular theory, if the coolant and / or diluent liquid 134 is dispensed radially inward from the polishing rate adjustment groove 120, the liquid may contact the substrate edge region before entering the groove 120. In the case where the liquid 134 is a coolant, the temperature of the polishing pad and the polishing liquid in the annular region 122 can be reduced, thereby reducing the polishing rate compared to the central region 124 radially inward from the annular region 122 . When the liquid 134 is a diluent, the concentration of the polishing liquid (eg, the concentration of chemicals and / or abrasive particles) in the annular region 122 can be reduced, thereby reducing the polishing rate. When the substrate 10 is positioned above the central region 124 of the polishing pad 30, the polishing surface 36 contacts and polishes the substrate 10, and material removal occurs. On the other hand, when the edge of the substrate 10 is positioned above the annular region 122, the polishing rate of the portion of the substrate above the annular region 122 is lower than the polishing rate of the portion of the substrate above the central region 124. 2A and 3 , for a first duration, the substrate 10 may be positioned in a first position or a first range of positions such that both the central portion 12 of the substrate 10 and the edge portion 14 of the substrate 10 are polished by the central region 124 and the polishing surface 36 of the polishing pad 30. Thus, the substrate 10 does not overlap the annular region 122. For the second duration, substrate 10 can be positioned such that central portion 12 of substrate 10 is polished by central region 124, and arcuate crescent-shaped region 14a of edge portion 14 of substrate 10 is above annular region 122. During the second duration, substrate 10 can remain laterally fixed in the second position. Thus, during the second duration, central portion 12 of substrate 10 is polished, while region 14a of edge portion 14 of substrate 10, positioned above annular region 122, is polished at a relatively lower polishing rate. Due to the rotation of substrate 10, edge portion 14 should still be polished in an angularly uniform manner, but at a lower average rate compared to central portion 12 due to the lower polishing rate in region 14a. The controller can cause the support to move carrier head 70 to laterally oscillate substrate 10 during the first duration, and to laterally hold substrate 10 in a fixed position for a period of time during the second duration. In order to reduce the removal of the edge portion 14 of the substrate 10 and obtain a more uniformly polished substrate 10, it may be determined to reduce the polishing area time fraction. For example, equation [1] may be used to determine the non-polishing area time fraction S 1: Where α is the angle of the annular region 122 across the substrate 10 relative to the center of the substrate and can be determined using equations [2] to [3]: and And wherein R1 is the radius of the inner edge of the annular region 122 , r is the radius of the substrate 10 , and x is the distance from the center of the polishing pad 30 to the center of the substrate 10 . The central portion 12 of the substrate 10 and the edge portion 14 of the substrate 10 are positioned over the central region 134 for a first duration T 1 (t 0 to t 1). The substrate may be moved laterally in an oscillatory manner during this first duration. At the end of the first duration, the substrate is repositioned. The central portion 12 of the substrate 10 is positioned above the central region 124, and the edge portion 14 of the substrate 10 is positioned and held above the annular region 122 for a second duration T. 2 (t 1 to t 2). The process may be repeated such that the substrate 10 oscillates between a first position (wherein the center portion and the edge portion of the substrate 10 are polished) for a first duration and a second position (wherein the substrate is held at the second position) for a second duration, where the center portion of the substrate 10 is polished and the edge portion of the substrate 10 is polished at a reduced rate for a duration calculated using the time share s. A first duration T may be selected 1 and the second duration T 2 in order to reduce the polishing rate of the edge portion 14 by a desired amount. For example, the ratio T 1 / T 2 to achieve a desired polishing rate at the edge, for example, to achieve the same polishing rate as the central portion 12. Ratio T 2 / (T 1+T 2) Provides the percentage of time per cycle where the substrate (eg, edge portion 14b) is positioned and held over the trench 102 (also known as dwell time), where a cycle is determined by the amount of time it takes for the substrate to return to the same position during one oscillation. Generally, if P does not use the polishing rate to adjust the polishing rate of the edge portion 14 of the groove, P' uses the polishing rate to adjust the polishing rate of the edge portion 14 of the groove, and P DES is the desired polishing rate, then the ratio T 2 / (T 1+T 2) It can be set as follows: FIG4A and FIG4B illustrate an embodiment in which the annular portion 130 of the polishing pad 30 has been replaced with a polishing material that is softer than the polishing material of the central region 124. For example, the annular portion 130 may be a porous polymer, such as a porous polyurethane. For example, the annular portion 130 may be a Suba IV or Politex polishing material. In some embodiments, the annular portion 130 may have the same material composition as the central region 124, but with a higher porosity, i.e., larger and denser pores, to provide a softer layer. As a result, the polishing rate of the annular portion 130 should be lower than that which would occur in the presence of the same polishing material. The annular portion 130 may have the same groove pattern as the central region 124 and may have grooves and lands that provide a portion of the polishing surface 36. As a result, when the meniscus portion 14a of the edge region 14 of the substrate 10 is positioned over the annular portion 130, the polishing rate of the edge region 14 should be reduced (compared to what would occur if the same polishing material were used across the entire polishing pad). The first polishing material in the central region 124 can have a hardness of 50 to 80 Shore D. For example, the first polishing material can include polyurethane, such as a porous polyurethane, such as a polyurethane having embedded hollow microspheres. The second polishing material in the annular portion 130 can have a hardness of 20 to 50 Shore D. The polishing surface of the central region 124 and the polishing surface of the annular portion 130 are coplanar. 4B , an annular portion 130 formed of the second polishing material may extend partially through the polishing layer 32. In this case, the annular portion 130 is supported on a thin section 134 formed of the first polishing material from the central region 124. Alternatively, the annular portion 130 and the second polishing material may extend completely through the polishing layer 32. The embodiment of Figures 4A and 4B can operate in a manner similar to that discussed above with respect to Figures 2A and 2B. That is, for a first duration, the substrate 10 can be positioned in a first position or a first range of positions such that both the central portion 12 of the substrate 10 and the edge portion 14 of the substrate 10 are polished by the central region 124 and the polishing surface 36 of the polishing pad 30. For a second duration, the substrate 10 can be positioned such that the central portion 12 of the substrate 10 is polished by the central region 124 and the arcuate crescent region 14a of the edge portion 14 of the substrate 10 is above the annular portion 130. Determine the first duration T 1 and the second duration T The ratio of 2 can also be determined in a similar manner as discussed above. 5A and 5B illustrate an embodiment in which the annular outer region 140 of the polishing pad 30 includes both circular polishing liquid distribution channels 110 and radially extending polishing liquid drain channels 142. The radially extending polishing liquid drain channels 142 serve to increase the flow of polishing liquid out of the annular outer region 140. Because less polishing liquid remains in the annular outer region 140, the polishing rate of the annular outer region 140 should be lower than would occur in the absence of the liquid drain channels 142. The polishing liquid drain grooves 142 may be distributed at equal angular intervals around the center of the polishing pad 30 (e.g., around the rotation axis 25). The polishing liquid drain grooves 142 may be wider and / or deeper than the polishing liquid distribution grooves 110. For example, the polishing liquid drain grooves 142 may have a width of 1 to 5 mm. The embodiment of Figures 5A and 5B can be operated in a manner similar to that discussed above with respect to Figures 2A and 2B and Figures 4A and 4B. That is, for a first duration, the substrate 10 can be positioned in a first position or a first range of positions such that both the central portion 12 of the substrate 10 and the edge portion 14 of the substrate 10 are polished by the central region 124 and the polishing surface 36 of the polishing pad 30. For a second duration, the substrate 10 can be positioned such that the central portion 12 of the substrate 10 is polished by the central region 124 and the arcuate crescent region 14a of the edge portion 14 of the substrate 10 is above the annular outer region 140 having the polishing liquid drainage grooves 142. Determining the first duration T 1 and the second duration T The ratio of 2 can also be determined in a similar manner as discussed above. Yet another technique that can be used in conjunction with any of the previous embodiments of Figures 2A-2B, 4A-4B, or 5A-5B is to use a retaining ring with a high density of polishing liquid channels. Figure 6 is a view of the bottom surface 82 of a retaining ring 80 surrounding a substrate 10. A plurality of channels 84 are formed as depressions in the bottom surface 82, extending from an inner diameter surface 86 to an outer diameter surface 88 of the retaining ring 80. The channels 84 can be distributed at substantially equal angular intervals around the center 89 of the retaining ring 80. All channels 84 can have the same shape, although they can be rotated as appropriate. The channel 84 is configured to allow the polishing liquid to flow easily between the inner diameter surface 86 and the outer diameter surface 88. For example, the channel 84 can be wide enough so that the channel 84 occupies at least half, e.g., 50 to 75%, of the surface area of ​​the bottom surface 82 in plan view. The large area of ​​the channel 84 can allow the slurry to flow easily away from the substrate edge 16, thereby reducing the polishing rate at the edge region 12. Furthermore, the channels 84 can be configured to preferentially direct polishing liquid from the interior of the retaining ring 80 to the exterior of the retaining ring 80 and away from the substrate edge 16 as compared to directing polishing liquid from the exterior toward the interior of the retaining ring 80 . For example, the passage 84 can be wider at the inner diameter surface 86 as compared to the outer diameter surface 88. In particular, the passage 84 can be flared at the inner diameter surface 86. As another example, the channels 84 can be tilted such that the major axis of each channel 84 (illustrated by dashed line A) is at an oblique angle α, e.g., 20 to 45°, relative to a radial segment (illustrated by dashed line R) extending from the center 88 of the retaining ring 80 to the corresponding channel 84. Specifically, the channels 84 are tilted from the inner diameter 86 to the outer diameter 84 in a direction opposite to the direction of rotation (illustrated by arrow B). For example, if the retaining ring 80 is rotated counterclockwise during a polishing operation, the channels extend clockwise from the inner diameter 86 to the outer diameter 84. Conversely, if the retaining ring 80 is rotated clockwise during a polishing operation, the channels extend counterclockwise from the inner diameter 86 to the outer diameter 84. Each channel 84 includes a leading edge 90 and a trailing edge 92. Without being limited to any particular theory, rotation of the retaining ring 80 causes the trailing edges 92 of the channels (which correspond to the leading edges of the lands 85 between the channels) to engage the polishing liquid, and the bevel of the trailing edges 92 pushes the polishing liquid outward. In the example shown in FIG. 6 , leading edge 90 includes an outer linear portion 90a adjacent to outer diameter surface 84. Similarly, trailing edge 92 includes an outer linear portion 92a adjacent to outer diameter surface 84. In this example, linear portions 90a, 92a are angled to form a portion 94 of a channel that tapers from the inside outward. Linear portions 90a, 92a may have an angle of 5 to 25 degrees. However, in some embodiments, linear portions 90a, 92a are parallel. Leading edge 90 also includes a portion 90b adjacent to inner diameter surface 84 that may be linear or curved but forms a greater angle with radial segment R than outer linear portion 90a. Similarly, trailing edge 92 also includes a portion 92b adjacent to inner diameter surface 84 that may be linear or curved but forms a smaller angle with radial segment R than outer linear portion 92a. This configuration can form a flared opening portion 96 at inner diameter surface 86 that widens more rapidly (from outside to inside) than portion 94. Either of these effects tends to cause the polishing liquid to flow away from the substrate edge 16 , thereby reducing the polishing rate at the edge region 12 . As used in this specification, the term substrate can include, for example, a production substrate (e.g., one that includes multiple memory or processor dies), a test substrate, a bare substrate, and a gated substrate. A substrate can be at various stages of IC fabrication; for example, a substrate can be a bare wafer, or it can include one or more deposited and / or patterned layers. The term substrate can also include circular disks and rectangular sheets. The polishing system and method described above can be applied to various polishing systems. The polishing pad, the carrier head, or both can be moved to provide relative motion between the polishing surface and the substrate. The polishing pad can be a round (or some other shaped) pad secured to a platform. The polishing layer can be a standard (e.g., polyurethane with or without fillers) polishing material, a soft material, or a fixed abrasive material. While the term relative positioning is used, it should be understood that the polishing surface and substrate can be held in a vertical orientation or some other orientation. While certain embodiments of the present 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 the desired results. 10: Substrate 12: Center portion 14: Edge portion 14a: Arched crescent region 16: Substrate edge 20: Chemical mechanical polishing system 24: Rotatable disc platform 25: Rotation axis 26: Motor 28: Drive shaft 30: Polishing pad 32: Outer polishing layer 34: Backing layer 36: Polishing surface 40: Pad conditioner device 42: Conditioning disk 44: Arm 50: Support structure 55: Shaft 56: Carrier head rotation motor 58: Drive shaft 62: Supply-rinse arm 64: Port 66: Polishing liquid 70: Carrier head 72: Housing 74: Flexible membrane 76a: Pressurizable chamber 76b: Pressurizable chamber 76c: Pressurizable chamber 80: Retaining ring 82: Bottom surface 84: Channel 85: Mesa 86: Inner diameter surface 89: Center 90: Front edge 90a: Outer linear portion 90b: Portion 92: Rear edge 92a: Outer linear portion 92b: Portion 94: Portion 96: Opening portion 100: Groove 110: Polishing liquid distribution groove 120: Polishing rate adjustment groove 122: Annular area 124: Central area 130: Annular portion 132: Outlet 134: Coolant and / or diluent liquid 140: Outer annular area 142: Polishing liquid discharge groove A: Dashed line B: Arrow R: Dashed line FIG. 1 is a schematic cross-sectional view of a chemical mechanical polishing system having a polishing pad with polishing rate adjustment grooves. FIG. 2A is a schematic top view of a polishing pad having polishing rate adjustment grooves concentric with the axis of rotation. FIG. 2B is a schematic cross-sectional view of a portion of the polishing pad of FIG. 2A having both slurry supply channels and polishing rate adjustment channels. FIG3 is a schematic diagram of substrate position on the stage versus time. FIG. 4A is a schematic top view of another embodiment of a polishing pad having an embedded buffing pad region. FIG. 4B is a schematic cross-sectional view of the polishing pad of FIG. 3A . FIG. 5A is a schematic top view of another embodiment of a polishing pad having radial grooves. FIG. 5B is a schematic cross-sectional view of the polishing pad of FIG. 3A . Figure 6 is a bottom view of the retaining ring. Like reference numbers and names in the various drawings indicate like elements. Domestic storage information (please note the order of storage institution, date and number) None Overseas deposit information (please note in the order of deposit country, institution, date, and number) None 10:Substrate 12: Center 14: Edge 14a: Arched crescent area 25: Rotation axis 30: Polishing pad 120: Polishing rate adjustment groove 122: Ring area 124: Central Area

Claims

1. A method for chemical mechanical polishing, the method comprising the steps of: rotating a polishing pad about a rotation axis; positioning a substrate against the polishing pad, the polishing pad having a polishing rate adjustment groove concentric with the rotation axis; dispensing a polishing liquid onto the polishing pad; dispensing a coolant, a diluent, or both into the polishing rate adjustment groove such that a polishing rate decreases in an annular region of the polishing pad positioned radially inward from the polishing rate adjustment groove, and wherein the annular region surrounds a central region of the polishing pad, in which a polishing rate is substantially unaffected by the coolant, diluent, or both; and laterally oscillating the substrate across the polishing pad such that, for a first duration, a central portion of the substrate and an edge portion of the substrate are positioned above the central region of the polishing pad, such that the central portion of the substrate... The edge portion of the substrate is polished by the central region of the polishing pad for the first duration, and for a second duration, the central portion of the substrate is held positioned above the central region of the polishing pad and an angled extension segment of the edge portion of the substrate is positioned above the annular region, such that the central portion of the substrate is polished by the central region of the polishing pad for the second duration, and the edge portion of the substrate is polished by both the central region and the annular region of the polishing pad for the second duration, so as to reduce the polishing rate of the edge portion.

2. The method as described in claim 1, wherein the step of dispensing a coolant, a diluent, or both comprises: dispensing the coolant.

3. The method as described in claim 2, wherein the coolant comprises a cooled polishing liquid.

4. The method as described in claim 2, wherein the coolant is purified deionized water.

5. The method as described in claim 1, wherein the step of dispensing a coolant, a diluent, or both comprises: dispensing the diluent.

6. The method as described in claim 5, wherein the diluent is purified deionized water.

7. The method as described in claim 1, comprising: holding the substrate in a lateral fixed position for the second duration.

8. The method as described in claim 1, wherein the polishing pad further comprises polishing liquid dispensing grooves.

9. The method as described in claim 8, wherein the polishing liquid distribution grooves are concentric with the polishing rate adjustment grooves.

10. The method as described in claim 8, wherein the polishing liquid distribution grooves are narrower than the polishing rate adjustment grooves.

11. The method as described in claim 1, wherein the polishing pad has a single polishing rate adjustment groove.

12. A polishing system comprising: a rotatable platform for supporting a polishing pad having a polishing rate adjustment groove concentric with a rotation axis of the platform; a first dispenser for delivering a polishing liquid onto the polishing pad; a second dispenser for dispensing a coolant, a diluent, or both into the polishing rate adjustment groove such that a polishing rate decreases in an annular region of the polishing pad radially inwardly positioned from the polishing rate adjustment groove, and wherein the annular region surrounds a central region of the polishing pad, in which a polishing rate is substantially unaffected by the coolant, diluent, or both; and a support head for holding a substrate against the polishing pad, the support head being laterally movable across the polishing pad. An actuator for moving the carrier head; and a controller coupled to the actuator and configured to cause the actuator to laterally oscillate the carrier head and the substrate across the polishing pad, such that, for a first duration, the actuator positions a central portion and an edge portion of the substrate above the central region of the polishing pad, such that the central portion and the edge portion of the substrate are polished by the central region of the polishing pad for the first duration, and for a second duration, the actuator positions the central portion of the substrate above the central region of the polishing pad and positions an angular extension of the edge portion of the substrate above the annular region, such that the central portion of the substrate is polished by the central region of the polishing pad for the second duration, and the edge portion of the substrate is polished by both the central region and the annular region of the polishing pad for the second duration, in order to reduce a polishing rate of the edge portion.

13. The system as claimed in claim 12, wherein the controller is configured to cause the actuator to hold the substrate in a lateral fixed position for the second duration.

14. The system as described in claim 12, wherein the second distributor is configured to dispense the coolant.

15. The system as claimed in claim 13, wherein the coolant comprises a cooled polishing liquid.

16. The system as described in claim 13, wherein the coolant is purified deionized water.

17. The system as described in claim 12, wherein the second dispenser is configured to dispense the diluent.

18. The system as described in claim 17, wherein the diluent is purified deionized water.

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