Trenches for edge and hot spot compensation in chemical mechanical polishing

Abstract

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

Description

Technical Field

[0001] This disclosure relates to chemical mechanical polishing of substrates. Background Technology

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconducting, or insulating layers on a silicon wafer. One fabrication 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 may be deposited on a patterned insulating layer to fill recesses or holes in the insulating layer. After planarization, 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. Furthermore, photolithography typically requires planarization of the substrate surface.

[0003] Chemical mechanical polishing (CMP) is a widely accepted planarization method. This planarization method typically requires mounting a substrate on a carrier or polishing head. The exposed surface of the substrate is usually placed against a rotating polishing pad. The carrier head provides a controlled load on the substrate to push it against the polishing pad. An abrasive polishing slurry is typically supplied to the surface of the polishing pad.

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

[0005] In one aspect, a method for chemical mechanical polishing includes: rotating a polishing pad about a rotation axis; positioning a substrate against the polishing pad; dispensing polishing fluid onto the polishing pad; and dispensing a coolant, a diluent, or both into a polishing rate adjusting groove concentric with the rotation axis, such that the polishing rate is reduced in an annular region radially inward of the polishing rate adjusting groove where the polishing pad is positioned. The annular region surrounds a central region of the polishing pad, in which the polishing rate is substantially unaffected by the coolant, diluent, or both. The substrate oscillates laterally 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 through 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 angularly extended segment of the edge portion of the substrate is positioned above the annular region, such that the central portion of the substrate is polished through the central region of the polishing pad for the second duration, and the edge portion of the substrate is polished through 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.

[0006] In another aspect, a polishing system includes: a rotatable platform for supporting a polishing pad having a polishing rate adjustment groove concentric with the platform's axis of rotation; a first distributor for delivering polishing fluid onto the polishing pad; a second distributor for delivering coolant, diluent, or both into the polishing rate adjustment groove, such that the polishing rate decreases in an annular region located radially inward of the polishing rate adjustment groove, wherein the annular region surrounds a central region of the polishing pad in which the polishing rate is substantially unaffected by the coolant, diluent, or both; a carrier head for holding a substrate against the polishing pad, the carrier head being laterally movable 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 laterally oscillate the carrier head and substrate across the polishing pad, such that for a first duration, the actuator positions the center portion and the edge portion of the substrate above the central region of the polishing pad, such that the center portion and the edge portion of the substrate are polished through the central region of the polishing pad for the first duration, and for a second duration, the actuator positions the center portion of the substrate above the central region of the polishing pad and positions an angular extension segment of the edge portion of the substrate above an annular region, such that the center portion of the substrate is polished through the central region of the polishing pad for the second duration, and the edge portion of the substrate is polished through both the central region and the annular region of the polishing pad for the second duration, in order to reduce the polishing rate of the edge portion.

[0007] On the other hand, a method for chemical mechanical polishing includes: rotating a polishing pad about a rotation axis; positioning a substrate against the polishing pad; dispensing polishing slurry onto the polishing pad; and dispensing a coolant, diluent, or both onto the polishing pad radially inward from but close to a polishing rate adjustment groove, the polishing rate adjustment groove being concentric with the rotation axis, such that the polishing rate is reduced in an annular region radially inward of the polishing rate adjustment groove at the polishing pad's positioning. The annular region surrounds a central region of the polishing pad, in which the polishing rate is substantially unaffected by the coolant, diluent, or both. The polishing rate adjustment groove is wider than the slurry distribution groove in the central portion of the polishing pad. The substrate oscillates laterally across the polishing pad, such that for a first duration, the central portion and the edge portion of the substrate are positioned above the central region of the polishing pad, and the central portion and the edge portion of the substrate are polished through the central region of the polishing pad for the first duration. For a second duration, the central portion of the substrate is held positioned above the central region of the polishing pad and the angular 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 through the central region of the polishing pad for the second duration, and the edge portion of the substrate is polished through both the central region and the annular region of the polishing pad for the second duration, in order to reduce the polishing rate of the edge portion.

[0008] In another aspect, a polishing system includes: a rotatable platform for supporting a polishing pad having a polishing rate adjustment groove concentric with the platform's axis of rotation; a first dispenser for delivering polishing fluid onto the polishing pad; a second dispenser for delivering coolant, diluent, or both onto the polishing pad at a location radially inward from but close to the polishing rate adjustment groove, such that the polishing rate decreases in an annular region of the polishing pad located radially inward of the polishing rate adjustment groove, wherein the annular region surrounds a central region of the polishing pad in which the polishing rate is substantially unaffected by the coolant, diluent, or both; a carrier head for holding a substrate against the polishing pad, the carrier head being laterally movable 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 laterally oscillate the carrier head and substrate across the polishing pad, such that for a first duration, the actuator positions the center portion and the edge portion of the substrate above the central region of the polishing pad, such that the center portion and the edge portion of the substrate are polished through the central region of the polishing pad for the first duration, and for a second duration, the actuator positions the center portion of the substrate above the central region of the polishing pad and positions an angular extension segment of the edge portion of the substrate above an annular region, such that the center portion of the substrate is polished through the central region of the polishing pad for the second duration, and the edge portion of the substrate is polished through both the central region and the annular region of the polishing pad for the second duration, in order to reduce the polishing rate of the edge portion.

[0009] The implementation may include, but is not limited to, one or more of the following advantages: Radial polishing non-uniformity can be controlled and corrected, for example, non-uniformity caused by different polishing rates at different portions of the substrate. For example, controlling the position of the substrate relative to areas with colder polishing slurry, diluted polishing slurry, or softer polishing pads 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 minimal. Polishing "hot spots" can be reduced, for example, limited angular areas at the edges of over-polished substrates.

[0010] Details of one or more implementations are set forth in the accompanying drawings and the following description. Other aspects, features, and advantages will be apparent from the description and drawings, as well as from the claims. Attached Figure Description

[0011] Figure 1 This is a schematic cross-sectional view of a chemical mechanical polishing system with a polishing pad having polishing rate adjustment grooves.

[0012] Figure 2AThis is a schematic top view of a polishing pad with polishing rate adjustment grooves concentric with the axis of rotation.

[0013] Figure 2B It has both slurry supply grooves and polishing rate adjustment grooves. Figure 2A A schematic cross-sectional view of a portion of the polishing pad.

[0014] Figure 3 It is a schematic diagram of the position of the substrate on the platform relative to time.

[0015] Figure 4A This is a schematic top view of another implementation of a polishing pad with an embedded polishing pad area.

[0016] Figure 4B yes Figure 3 A schematic cross-sectional view of the polishing pad of A.

[0017] Figure 5A This is a schematic top view of another implementation of a polishing pad with radial grooves.

[0018] Figure 5B yes Figure 3 A schematic cross-sectional view of the polishing pad of A.

[0019] Figure 6 This is a bottom view of the retaining ring.

[0020] The same component symbols and names in each figure indicate the same component. Detailed Implementation

[0021] As mentioned above, when polishing a substrate with a polishing pad, the edge portions of the substrate can be polished at a higher rate than the center portions, resulting in an unevenly polished substrate. Furthermore, polishing "hot spots" may occur, such as over-polished angular areas at the edges of the substrate.

[0022] However, several techniques can be used to reduce the polishing rate at substrate edges and / or reduce polishing hotspots. These techniques can be used alone or in combination.

[0023] On one hand, cold liquid or diluent can be dispensed into the polishing rate adjustment trench, and the substrate can be positioned with its edges adjacent to the polishing rate adjustment trench. Cold liquid or diluent can flow from the polishing rate adjustment trench below the edge portion of the substrate, thus reducing the polishing rate at the substrate edge.

[0024] On the other hand, the outer annular portion of the polishing pad can be replaced with a material that is softer and has a lower polishing rate compared to the polishing material in the central portion of the polishing pad. The substrate can be positioned with its edge above this annular region to reduce the polishing rate at the substrate edge.

[0025] On the other hand, trenches can be placed on the polishing pad, and these trenches will preferentially guide the polishing slurry away from the 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 substrate edge.

[0026] On the other hand, retaining rings with high-density slurry distribution channels can be used for polishing substrates with high edge polishing rates. The slurry distribution channels can be configured to preferentially guide the polishing slurry away from the substrate. This can reduce the polishing rate at the substrate edges.

[0027] Figure 1 An example of a polishing station for a chemical mechanical polishing system 20 is shown. The polishing system 20 includes a rotatable disc-shaped platform 24 on which a polishing pad 30 is positioned. The platform 24 is operable to rotate about an axis 25. For example, a motor 26 can rotate a drive shaft 28 to rotate the platform 24. The polishing pad 30 may be a two-layer polishing pad having an outer polishing layer 32 and a softer backing layer 34. The outer polishing layer 32 has a polishing surface 36.

[0028] Multiple grooves 100 may be formed in the polished surface 36. In some implementations, the multiple grooves 100 include both multiple polishing slurry distribution grooves 110 and polishing rate adjustment grooves 120. In some implementations, the multiple grooves 100 include only polishing slurry distribution grooves 110.

[0029] The slurry distribution grooves 110 may be annular grooves, such as circular grooves, and may be concentric with the center of the polishing pad 30, for example, with the axis of rotation 25. Alternatively, the slurry distribution grooves 110 may have another pattern, such as rectangular crosshairs, triangular crosshairs, etc. The slurry distribution grooves 110 may have a width, such as 0.20 inches, between about 0.015 and 0.04 inches (between 0.381 and 1.016 mm), and a spacing, such as 0.12 inches, between about 0.09 and 0.24 inches. The slurry distribution grooves 110 may be evenly spaced across the polishing pad 30.

[0030] The polishing system 20 may include a supply arm or a combined supply-rinse arm 62 having a port 64 for dispensing polishing fluid 66 (such as abrasive slurry) onto the polishing pad 30. The port 64 may be positioned close to the axis of rotation 25 such that centrifugal force carries the polishing fluid outward across the polishing surface 36.

[0031] The polishing system 20 may include a pad adjuster device 40 with an adjusting disk 42 to maintain the surface roughness of the polishing surface 36 of the polishing pad 30. The adjusting disk 42 may be positioned at the end of an arm 44, which may swing to radially sweep the disk 42 across the polishing pad 30.

[0032] The carrier head 70 is operable to hold the substrate 10 against the polishing pad 30. The carrier head 70 is suspended on 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, allowing the carrier head to rotate about an axis 55. Depending on the situation, the carrier head 70 can oscillate laterally, for example, by sliding on a slide on the turntable, by moving along a track, or by the rotational oscillation of the turntable itself.

[0033] 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 fixed to the housing 72. In operation, the bottom surface 82 of the retaining ring 80 contacts the polishing surface 36. Depending on the application, multiple channels may be formed in the bottom surface 82 of the retaining ring 80 to allow polishing fluid 66 to flow between the inside and outside 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 a drive shaft 58 to rotate with it during polishing. A passage (not shown) extending through the housing 72 may be present for pneumatic control of the carrier head 70.

[0034] Figure 1 , Figure 2A ,and Figure 2B One embodiment is shown 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 may be an annular groove, for example, circular, and may be concentric with the axis of rotation 25. The polishing rate adjustment groove 120 may be distributed around the polishing fluid as grooves 110 (for ease of illustration, in...). Figure 2A The polishing slurry distribution groove 110 is not shown in the diagram, but... Figure 2B (As shown in the figure). Assuming the polishing slurry distribution groove 110 is a circular groove, the polishing rate adjustment groove 120 may be concentric with the polishing slurry distribution groove 110. In some embodiments, there is no additional polishing slurry distribution groove 110 radially outward from the polishing rate adjustment groove 120.

[0035] 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 implementations the bottom surface of the polishing rate adjustment groove 120 may be angled or U-shaped. The depth of the polishing rate adjustment groove 120 may be 10 to 80 mils, for example, 10 to 60 mils. The polishing rate adjustment groove 120 may have a width of three to fifty, for example, five to fifty, three to ten, for example, ten to twenty millimeters.

[0036] In some implementations, 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, or, for example, within 10% (by radius). For example, the polishing rate adjustment groove 120 may be located at a radial distance of fourteen inches from the center of a thirty-inch diameter table.

[0037] The slurry distribution groove 110 is narrower than the polishing rate adjustment groove 120. For example, the slurry distribution groove 110 may be at least 3 times narrower, for example, at least 6 times narrower, such as 6 to 10 times narrower. The polishing rate adjustment groove 120 may have a smaller, similar, or larger depth compared to the slurry distribution groove 110. In some implementations, the polishing rate adjustment groove 120 is the only groove on the polishing pad 30 that is wider than the slurry distribution groove 110.

[0038] See Figure 1 In embodiments including the polishing rate adjustment groove 120, the polishing system 20 includes a dispenser 130 with an outlet 132 to deliver a liquid 134 that acts as a coolant, or a diluent, or both (see [link to documentation]). Figure 1 Specifically, outlet 132 may be positioned directly above polishing rate adjustment groove 120, such that liquid 134 flows directly into polishing rate adjustment groove 120. Alternatively, outlet 132 may be positioned such that liquid 134 flows onto the polishing surface. For example, outlet 132 may be positioned such that liquid 134 is dispensed radially inward from polishing rate adjustment groove 120 but close to it (e.g., within 10 cm, or for example, within 5 cm).

[0039] Assuming liquid 134 is a coolant, the liquid coolant could be polishing fluid 66, but cooled to, for example, 0 to 5°C. Alternatively, the liquid coolant could 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 outlet 132.

[0040] Assuming liquid 134 is a diluent, the liquid diluent can be deionized (DI) water. In this case, the liquid diluent can be distributed at room temperature (e.g., 20 to 23°C).

[0041] See Figure 2ADistributing coolant and / or diluent into the polishing rate adjustment trench 120 creates an annular region 122 extending radially inward from and immediately adjacent to the polishing rate adjustment trench 120, wherein 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 trench 120, but centrifugal force can limit the diffusion of coolant and / or diluent liquid 134 inward from the polishing rate adjustment trench 120. Still without being limited to any particular theory, if the coolant and / or diluent liquid 134 is distributed at a location radially inward from the polishing rate adjustment trench 120, the liquid may contact the substrate edge region before falling into the trench 120.

[0042] When liquid 134 is a coolant, the temperature of the polishing pad and polishing fluid 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.

[0043] When liquid 134 is a diluent, the concentration of polishing fluid (e.g., the concentration of chemicals and / or abrasive particles) in the annular region 122 can be reduced, thereby reducing the polishing rate.

[0044] 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.

[0045] See now Figure 2A and Figure 3 For the first duration, the substrate 10 can be positioned in a first position or within a first position range, such that the central portion 12 and the edge portion 14 of the substrate 10 are both polished by the central region 124 and the polishing surface 36 of the polishing pad 30. Therefore, neither substrate 10 overlaps with the annular region 122.

[0046] For the second duration, the substrate 10 can be positioned such that the central portion 12 of the substrate 10 is polished through the central region 124, and the crescent-shaped region 14a of the edge portion 14 of the substrate 10 is above the annular region 122. During the second duration, the substrate 10 can be held laterally fixed in the second position. Therefore, during the second duration, the central portion 12 of the substrate 10 is polished, while the region 14a of the edge portion 14 of the substrate 10 positioned above the annular region 122 is polished at a relatively low polishing rate. Due to the rotation of the substrate 10, the edge portion 14 should still be polished in an angularly uniform manner, but due to the lower polishing rate in region 14a, it is polished at a lower average rate compared to the central portion 12. The controller can cause the support to move the carrier head 70 during the first duration to cause the substrate 10 to oscillate laterally, and to hold the substrate 10 in a fixed position laterally for a period of time during the second duration.

[0047] In order to reduce the removal of the edge portion 14 of the substrate 10 and obtain a more uniformly polished substrate 10, the time share of the polished area can be determined. For example, equation [1] can be used to determine the time share S1 of the unpolished area: [1] Where α is the angle between the annular region 122 and the center of the substrate across the substrate 10, and can be determined using equations [2] to [3]: [2] and [3] And 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.

[0048] The central portion 12 and the edge portion 14 of the substrate 10 are positioned above the central region 134 for a first duration T1 (t0 to t1). The substrate may move laterally in an oscillating 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 T2 (t1 to t2).

[0049] The process can be repeated such that the substrate 10 oscillates between a first position (where the center portion and edge portion of the substrate 10 are polished) for a first duration and a second position (where the substrate is held in the second position) for a second duration, at which the center portion of the substrate 10 is polished and the edge portion of the substrate 10 is polished at a decreasing rate for a duration calculated using time fractions.

[0050] 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. For example, the ratio T1 / T2 can be selected to achieve a desired polishing rate at the edge, for example, to achieve the same polishing rate as the center portion 12.

[0051] The ratio T2 / (T1+T2) provides the percentage of time for each cycle, where the substrate (e.g., edge portion 14b) is positioned and held above the trench 102 (also known as dwell time), and the cycle is determined by the amount of time it takes for the substrate to return to the same position during one oscillation.

[0052] Typically, if P is the polishing rate of the edge portion 14 of the trench without using the polishing rate adjustment, then P' is the polishing rate of the edge portion 14 of the trench using the polishing rate adjustment, and P DES If the desired polishing rate is given, then the ratio T2 / (T1+T2) can be set as follows: [4] Figure 4A and Figure 4B One embodiment is shown 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 porous polyurethane. For example, the annular portion 130 may be a Suba IV or Politex polishing material. In some implementations, the annular portion 130 may have the same material composition as the central region 124, but with 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 the polishing rate that 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 mesa providing a portion of the polished surface 36.

[0053] As a result, when the crescent-shaped portion 14a of the edge region 14 of the substrate 10 is positioned above the annular portion 130, the polishing rate of the edge region 14 should be reduced (compared to the polishing rate that would occur if the same polishing material were used across the entire polishing pad).

[0054] 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 porous polyurethane, such as polyurethane with embedded hollow microspheres. The second polishing material in the annular portion 130 can have a hardness of 20 to 50 Shore D. The polished surfaces of the central region 124 and the annular portion 130 are coplanar.

[0055] like Figure 4B As shown, the annular portion 130 formed by the second polishing material can partially extend through the polishing layer 32. In this case, the annular portion 130 is supported on a thin segment 134 formed by the first polishing material from the central region 124. Alternatively, the annular portion 130 and the second polishing material can extend completely through the polishing layer 32.

[0056] Figure 4A and Figure 4B The embodiments can be similar to those described above for... Figure 2A and Figure 2B The author operates in a similar manner. That is, for the first duration, the substrate 10 can be positioned in a first position or within a first position range such that both the central portion 12 and the edge portion 14 of the substrate 10 are polished through the central region 124 of the polishing pad 30 and the polishing surface 36. For the second duration, the substrate 10 can be positioned such that the central portion 12 of the substrate 10 is polished through the central region 124, and the crescent-shaped region 14a of the edge portion 14 of the substrate 10 is above the annular portion 130. The ratio of the first duration T1 to the second duration T2 can also be determined in a manner similar to that described above.

[0057] Figure 5A and Figure 5B One embodiment is shown in which the annular outer region 140 of the polishing pad 30 includes both a circular polishing slurry distribution channel 110 and a radially extending polishing slurry discharge channel 142. The radially extending polishing slurry discharge channel 142 is used to increase the flow rate of polishing slurry leaving the annular outer region 140. Because less polishing slurry is retained in the annular outer region 140, the polishing rate of the annular outer region 140 should be lower than the polishing rate that would occur without the liquid discharge channel 142.

[0058] The polishing slurry discharge channels 142 may be distributed at equal angular intervals around the center of the polishing pad 30 (e.g., around the axis of rotation 25). The polishing slurry discharge channels 142 may be wider and / or deeper than the polishing slurry distribution channels 110. For example, the polishing slurry discharge channels 142 may have a width of 1 to 5 mm.

[0059] Figure 5A and Figure 5B The embodiments can be similar to those described above for... Figure 2A and Figure 2B as well as Figure 4A and Figure 4BThe author operates in a similar manner. That is, for the first duration, the substrate 10 can be positioned in a first position or within a first position range such that both the central portion 12 and the edge portion 14 of the substrate 10 are polished through the central region 124 of the polishing pad 30 and the polishing surface 36. For the second duration, the substrate 10 can be positioned such that the central portion 12 of the substrate 10 is polished through the central region 124, and the crescent-shaped region 14a of the edge portion 14 of the substrate 10 lies on the annular outer region 140 having the polishing fluid discharge groove 142. The ratio of the first duration T1 to the second duration T2 can also be determined in a manner similar to that described above.

[0060] Can be with Figures 2A-2B , Figures 4A-4B ,or Figures 5A-5B Another technique used in combination with any of the previous embodiments is the use of a retaining ring with high-density polishing fluid channels. Figure 6 This is a view of the bottom surface 82 of the retaining ring 80 surrounding the substrate 10. A plurality of channels 84 are formed as recesses in the bottom surface 82, extending from the inner diameter surface 86 of the retaining ring 80 to the outer diameter surface 88. The channels 84 may be distributed at substantially equal angular intervals around the center 89 of the retaining ring 80. All channels 84 may have the same shape, although they may be rotatable.

[0061] Channel 84 is configured to allow polishing slurry to flow easily between the inner diameter surface 86 and the outer diameter surface 88. For example, channel 84 may be wide enough that it occupies at least half, for example, 50 to 75%, of the surface area of ​​the bottom surface 82 in a plan view. The large area of ​​channel 84 allows the slurry to flow easily from the substrate edge 16, thereby reducing the polishing rate at the edge region 12.

[0062] Furthermore, rather than guiding the polishing slurry from the outside of the retaining ring 80 toward the inside of the retaining ring 80, the channel 84 can be configured to preferentially guide the polishing slurry from the inside of the retaining ring 80 to the outside of the retaining ring 80 and away from the substrate edge 16.

[0063] For example, channel 84 may be wider at inner diameter surface 86 than outer diameter surface 88. Specifically, channel 84 may be flared at inner diameter surface 86.

[0064] As another example, channels 84 can be tilted such that the main axis of each channel 84 (shown by dashed line A) forms an angle α with respect to a radial segment (shown by dashed line R), for example, 20 to 45°, which extends from the center 88 of the retaining ring 80 to the corresponding channel 84. Specifically, channels 84 are tilted from the inner diameter 86 to the outer diameter 84 in the direction opposite to the direction of rotation (shown by arrow B). For example, if the retaining ring 80 rotates 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 rotates clockwise during a polishing operation, the channels extend counterclockwise from the inner diameter 86 to the outer diameter 84.

[0065] Each channel 84 includes a front edge 90 and a rear edge 92. Without being limited to any particular theory, the rotation of the retaining ring 80 causes the rear edge 92 of the channel (which corresponds to the front edge of the platform 85 between the channels) to engage the polishing fluid, and the bevel of the rear edge 92 pushes the polishing fluid outward.

[0066] exist Figure 6 In the example shown, the leading edge 90 includes an outer linear portion 90a adjacent to the outer diameter surface 84. Similarly, the trailing edge 92 includes an outer linear portion 92a adjacent to the outer diameter surface 84. In this example, the linear portions 90a and 92a are angled to form a portion 94 of a channel that gradually narrows from the inside out. The linear portions 90a and 92a can have an angle of 5 to 25°. However, in some implementations, the linear portions 90a and 92a are parallel.

[0067] The leading edge 90 also includes a portion 90b adjacent to the inner diameter surface 84, which may be linear or curved, but forms a larger angle with the radial segment R compared to the outer linear portion 90a. Similarly, the trailing edge 92 also includes a portion 92b adjacent to the inner diameter surface 84, which may be linear or curved, but forms a smaller angle with the radial segment R compared to the outer linear portion 92a. This configuration may form a flared opening 96 at the inner diameter surface 86, which widens more rapidly (from the outside in) compared to portion 94.

[0068] Any of these effects tends to cause the polishing slurry to flow away from the substrate edge 16, thus reducing the polishing rate at the edge region 12.

[0069] As used in this specification, the term substrate can include, for example, a product substrate (e.g., comprising multiple memory or processor dies), a test substrate, a bare substrate, and a gated substrate. The substrate can be at various stages of integrated circuit manufacturing; for example, the substrate can be a bare wafer, or it can include one or more deposited layers and / or patterned layers. The term substrate can include circular disks and rectangular wafers.

[0070] The polishing systems and methods described above can be applied to a variety of polishing systems. The polishing pad, or carrier head, or both, can be movable to provide relative movement between the polishing surface and the substrate. The polishing pad can be a circular (or some other shape) pad fixed 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. Using the terminology of relative positioning, it should be understood that the polishing surface and the substrate can be held in a vertical orientation or some other orientation.

[0071] Specific embodiments of the invention have been described. Other embodiments are within the scope of the appended claims. For example, the actions described in the claims can be performed in a different order and still achieve the desired result.

Claims

1. A method for chemical mechanical polishing, the method comprising: Rotate the polishing pad around the axis of rotation; The polishing pad is positioned against the polishing pad positioning substrate, and the polishing pad has a polishing rate adjustment groove concentric with the rotation axis; Dispense the polishing fluid onto the polishing pad; A coolant, a diluent, or both are dispensed into the polishing rate adjustment groove such that the polishing rate is reduced in an annular region located radially inside the polishing rate adjustment groove of the polishing pad, and wherein the annular region surrounds a central region of the polishing pad in which the polishing rate is substantially unaffected by the coolant, diluent, or both. as well as The substrate is oscillated laterally across the polishing pad, such that... For a first duration, the central portion of the substrate and the edge portion of the substrate are positioned above the central region of the polishing pad, such that the central portion of the substrate and the edge portion of the substrate are polished through the central region of the polishing pad for the first duration. For the second duration, the central portion of the substrate is held positioned above the central region of the polishing pad and the 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 through the central region of the polishing pad for the second duration, and the edge portion of the substrate is polished through both the central region and the annular region of the polishing pad for the second duration, in order to reduce the polishing rate of the edge portion.

2. The method of claim 1, wherein the dispensing coolant, diluent, or both comprises: Dispense the coolant.

3. The method of claim 2, wherein the coolant comprises a cooled polishing fluid.

4. The method of claim 2, wherein the coolant is purified deionized water.

5. The method of claim 1, wherein the dispensing coolant, diluent, or both comprises: Dispense the diluent.

6. The method of claim 5, wherein the diluent is purified deionized water.

7. The method of claim 1, comprising: The substrate is held in a laterally fixed position for the second duration.

8. The method of claim 1, wherein the polishing pad further comprises polishing fluid distribution grooves.

9. The method of claim 8, wherein the polishing slurry distribution groove is concentric with the polishing rate adjustment groove.

10. The method of claim 3, wherein the polishing slurry distribution groove is narrower than the polishing rate adjustment groove.

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

12. A polishing system, comprising: A rotatable table for supporting a polishing pad, the polishing pad having a polishing rate adjustment groove concentric with the rotation axis of the table; A first dispenser is used to deliver polishing slurry to the polishing pad; A second distributor is used to dispense coolant, diluent, or both into the polishing rate adjusting groove, such that the polishing rate is reduced in an annular region where the polishing pad is positioned radially inside the polishing rate adjusting groove, and wherein the annular region surrounds a central region of the polishing pad in which the polishing rate is substantially unaffected by the coolant, diluent, or both. A carrier head is used to hold the substrate against the polishing pad, and the carrier head can move laterally across the polishing pad; An actuator for moving the carrier head; as well as 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 the center portion and the edge portion of the substrate above the central region of the polishing pad, such that the center portion and the edge portion of the substrate are polished through the central region of the polishing pad for the first duration. For the second duration, the actuator positions the center portion of the substrate above the central region of the polishing pad and positions the angular extension segment of the edge portion of the substrate above the annular region, such that the center portion of the substrate is polished through the central region of the polishing pad for the second duration, and the edge portion of the substrate is polished through both the central region of the polishing pad and the annular region for the second duration, in order to reduce the polishing rate of the edge portion.

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

14. The system of claim 12, wherein the second dispenser is configured to dispense the coolant.

15. The system of claim 13, wherein the coolant comprises a cooled polishing fluid.

16. The system of claim 13, wherein the coolant is purified deionized water.

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

18. The system of claim 17, wherein the diluent is purified deionized water.

Images