Polishing system with non-contact platen edge control

Abstract

The polishing system includes a platen having an upper surface supporting a primary polishing pad. The platen is rotatable about an axis of rotation passing through approximately the center of the platen. An annular flange projects radially outward from the platen to support an outer polishing pad. The annular flange is fixed to the platen for rotation therewith and has an inner edge fixed perpendicular to the upper surface of the platen. The annular flange is vertically deflectable such that the outer edge of the annular flange is movable perpendicular to the inner edge. An actuator applies pressure to an underside of the annular flange in an angularly limited area, and a carrier head is movable to hold a substrate in contact with the polishing pad and selectively position a portion of the substrate on the outer polishing pad.

Description

[Technical field]

[0001] SUMMARY The present disclosure relates to chemical mechanical polishing of a substrate by controlling the pressure applied by a platen. [Background technology]

[0002] Integrated circuits are typically formed on substrates by sequentially depositing conductive, semiconductive, and insulating layers on a silicon wafer. One manufacturing step involves depositing a fill layer over an uneven 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 the 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 over the uneven surface. Additionally, photolithography typically requires planarization of the substrate surface.

[0003] Chemical mechanical polishing (CMP) is an accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is then applied to a polishing pad, which typically rotates. The carrier head provides a controllable load on the substrate, forcing it against the polishing pad. An abrasive slurry is typically applied to the surface of the polishing pad. Summary of the Invention

[0004] In one aspect, a polishing system includes a platen having an upper surface supporting a primary polishing pad. The platen is rotatable about an axis of rotation passing through approximately the center of the platen. An annular flange projects radially outward from the platen to support an outer polishing pad. The annular flange is secured to the platen and rotatable therewith, and has an inner edge fixed perpendicular to the upper surface of the platen. The annular flange is vertically deflectable such that the outer edge of the annular flange is movable perpendicular to the inner edge. An actuator applies pressure to an underside of the annular flange in an angularly limited area, and a carrier head is movable to hold a substrate in contact with the polishing pad and selectively position a portion of the substrate on the outer polishing pad.

[0005] Implementations may optionally include one or more of the following advantages, but are not limited to these.

[0006] The described technique allows for non-contact control, i.e., the actuator can control the vertical position of the annular flange of the platen or the upward pressure of the annular flange against the polishing pad and the substrate without any physical contact between the actuator and the annular flange. Compared to techniques that require the actuator to contact the annular flange to apply pressure, fewer particles are generated, which may reduce the likelihood of defects.

[0007] The described technique can reduce polishing non-uniformities, especially at the edge of the substrate, by applying respective pressure to the edge of the substrate during polishing to increase or decrease the polishing rate at the edge, such that the substrate has a uniform polished thickness at the end of the polishing process.

[0008] 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]

[0009] [Figure 1] 1 is a schematic cross-sectional view of an example chemical mechanical polishing system. [Diagram 2] FIG. 2 is a schematic top view illustrating an example of the chemical mechanical polishing system of FIG. [Diagram 3] FIG. 1 is a perspective view of an example chemical mechanical polishing system. [Figure 4] 1 is a schematic cross-sectional view of an example chemical mechanical polishing system including a non-contact actuator having a permanent magnet. [Diagram 5] 1 is a schematic cross-sectional view of an example chemical mechanical polishing system including a non-contact actuator having an electromagnet. [Figure 6] 1 is a schematic cross-sectional view of an example chemical mechanical polishing system including a non-contact actuator having a fluid ejection nozzle.

[0010] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In some chemical mechanical polishing processes, portions of a substrate may be under-polished or over-polished. In particular, the substrate may be prone to being over- or under-polished at or near the edge of the substrate, e.g., a strip located 0-10 mm from the edge of the substrate. One technique to address such polishing non-uniformities is to transfer the substrate to a separate "touch-up" tool to, for example, perform edge correction. However, the additional tool consumes valuable footprint in the cleanroom and may adversely affect throughput.

[0012] A proposed solution to this problem is to provide an integrated polishing station in which an actuator contacts the annular flange and deflects the flange upwards to increase pressure on the substrate edge. However, when the actuator contacts the annular flange, particles can be generated, for example due to friction between solid parts. These particles can contaminate the substrate and / or the clean room and cause defects. However, these problems can be addressed by employing a non-contact actuator that exerts pressure on the annular flange without physical contact between the solid parts.

[0013] 1 and 2 illustrate an exemplary polishing system 20 operable to polish a substrate 10. The polishing system 20 includes a rotatable platen 24 on which a primary polishing pad 30 is positioned.

[0014] The platen is operable to rotate about an axis 25. For example, a motor 21 can rotate a drive shaft 22 to rotate the platen 24. In some implementations, the platen 24 is configured to provide an annular top surface 28 that supports a primary polishing pad 30. In some implementations, an aperture 26 is formed in the top surface 28 at the center of the platen 24. The center of the aperture 26 can be aligned with the axis of rotation 25. For example, the aperture 26 can be circular and the center of the aperture 26 can be coaxial with the axis of rotation 25. If the platen 24 has an annular top surface, a hole 31 can be formed through the primary polishing pad 30 to give the polishing pad an annular shape.

[0015] In some implementations, aperture 26 is a recess that extends partially but not entirely through platen 24. In some implementations, aperture 26 extends completely through platen 24, e.g., aperture 26 provides a passageway through platen 24. As shown in FIG. 1, aperture 26 may also provide an outlet for polishing residue (e.g., polishing fluid 38 or debris from the polishing process). Conduit 29 may drain polishing residue from recesses that do not extend entirely through platen 24.

[0016] The diameter of the aperture 26 (e.g., adjacent the surface 28 as a recess or as the top of a passageway through the platen 24) may be about 5% to 40%, such as about 5% to 15%, or 20% to 30%, of the diameter of the platen 24. For example, for a 30 to 42 inch diameter platen, the diameter may be 3 to 12 inches.

[0017] However, aperture 26 in platen 24 and hole 31 in polishing pad 30 are optional, and both polishing pad 30 and platen 24 may be solid circular bodies with circular upper surfaces.

[0018] The primary polishing pad 30 may be secured to the upper surface 28 of the platen 24 by, for example, a layer of adhesive. When worn, the primary polishing pad 30 may be removed and replaced. The primary polishing pad 30 may be a two-layer polishing pad having an outer polishing layer 32 having a polishing surface 36 and a softer backing layer 34. If the primary polishing pad 30 is annular, it has an inner edge that defines the perimeter of the aperture 26 through the pad 30. The inner edge of the pad 30 may be circular.

[0019] The polishing system 20 may include a pad cleaning system, such as a polishing fluid supply arm 39 and / or a rinsing fluid supply arm. During polishing, the arm 39 is operable to dispense a polishing fluid 38, such as a slurry containing abrasive particles. In some implementations, the polishing system 20 includes a combined slurry / rinsing arm. Alternatively, the polishing system may include a port in the platen operable to dispense a polishing fluid onto the primary polishing pad 30.

[0020] The polishing system 20 includes a carrier head 70 operable to hold the substrate 10 against the primary polishing pad 30. The carrier head 70 is suspended from a support structure 72, e.g., a carousel or track, and is connected to a carrier head rotation motor 76 by a carrier drive shaft 74 such that the carrier head can rotate about an axis 71. In addition, the carrier head 70 can oscillate laterally across the polishing pad, e.g., by moving a radial slot in the carousel driven by an actuator, by rotating the carousel driven by a motor, or by moving back and forth along the track driven by an actuator. In operation, the platen 24 rotates about its central axis 25, and the carrier head rotates about its central axis 71 and translates laterally across the top surface of the polishing pad.

[0021] The polishing system 20 may also include a conditioner system 40 having a rotatable conditioner head 42, which may include an abrasive underside, for example, on a removable conditioning disk, for conditioning the polishing surface 36 of the primary polishing pad 30. The conditioner system 40 may also include a motor for driving the conditioner head 42. 45 and a drive shaft 46 connecting the motor to the conditioner head 42. The conditioner system 40 may also include an actuator configured to sweep the conditioner head 42 laterally across the primary polishing pad 30, the outer polishing pad 56, and the optional inner polishing pad 66.

[0022] The polishing system 20 also includes at least one annular flange secured to the platen and rotating therewith. A portion of the inner or outer polishing pad rests on the flange, and the flange is deformable by an actuator such that an angularly limited section of the inner or outer polishing pad is biased against the bottom surface of the substrate. The annular flange may project outward from the outer edge of the platen, may project inward from the inner edge of the annular platen, or there may be two flanges, one at each position.

[0023] As shown in the embodiment of Figures 1 and 2, the polishing system 20 includes an annular flange 50 that protrudes radially outward from the platen 24. When not deflected or deformed, the upper surface of the annular flange 50 is substantially flush with the upper surface 38 of the platen 24. An inner edge of the annular flange 50 is fixed to the platen 24 and is rotatable therewith. Thus, the annular flange 50 can rotate with the platen 24 when the drive shaft 22 rotates the platen 24 (thus, the annular flange 50 does not require a separate motor for rotation). The annular flange 50 can be a deflectable elastic material. For example, the annular flange can be made of PTFE.

[0024] The inner edge of the annular flange 50 is fixed perpendicular to the upper surface of the platen 24. However, the annular flange 50 is vertically deflectable such that the outer edge of the annular flange 50 is movable perpendicular to the inner edge of the annular flange 50. In particular, the polishing system 20 includes a non-contact actuator 51 that applies pressure to the underside of the annular flange 50 in the angularly limited region 44 to deform a segment of the outer polishing pad 56, i.e., the actuator 51 can apply pressure to the annular flange 50 without physically contacting the annular flange 50.

[0025] The polishing system 20 may include an outer polishing pad 56 supported by and secured to the annular flange 50. The outer polishing pad 56 may be used to perform corrective polishing on a substrate, such as an edge of the substrate 10 or a portion of the substrate 10 near the edge. The outer polishing pad 56 may have a layer structure similar to that of the primary polishing pad 30, such as a polishing layer supported on a backing layer.

[0026] The outer polishing pad 56 may be angularly segmented. Referring to FIG. 2, the otherwise annular outer polishing pad 56 may be divided into angular pad segments 58 by channels 57. The channels 57 may be equally angularly spaced around the axis of rotation of the platen, and the segments 58 may have equal arc lengths. FIG. 2 illustrates eight channels 57 dividing the outer polishing pad into eight segments 58, but there may be more or fewer channels 57 and segments 58. The channels 57 may also be used to drain polishing by-products, such as slurry 38 or debris from the polishing process. Pad segments 58 that are not below the substrate 10 may be conditioned by the conditioning system 40 while rotating about the axis of rotation 25 of the platen 24.

[0027] The polishing surface of the outer polishing pad 56 may be separated from the primary polishing pad 30 by a gap 55. A channel 57 may extend to the gap 55 so that polishing residue (e.g., polishing slurry 38 or debris from the polishing process) may be drained from the channel 57 into the gap 55. One or more conduits 59 having openings in the gap 55 may allow the polishing residue to be drained from the gap 55 (see FIGS. 4-7).

[0028] The outer polishing surface 54 of the outer polishing pad 56 may be annular and may be concentric with the axis of rotation 25 of the platen. In some implementations, the outer polishing pad 56 includes an annular ridge extending upward from the lower layer (see FIG. 5A). The channels 57 may divide the annular ridge into a number of arcs 53. The upper surface of the annular ridge provides the outer polishing surface 54. Each arc 53 may have a width w (measured along the radius of the platen). The width w may be angularly uniform along the arcs 53. Each arc may have the same dimensions, or the width w may vary from arc 53 to arc 53. The width w is sufficiently small to allow the outer polishing pad 56 to perform corrective polishing on a narrow portion of the substrate 10, e.g., an area between 1 and 30 mm wide, e.g., an area between 1 and 10 mm wide, e.g., an area between 5 and 30 mm wide (e.g., on a circular substrate with a diameter of 300 mm).

[0029] The annular protrusion may have a rectangular cross-section (perpendicular to the top surface of the flange or polishing surface 36). The sidewalls of the annular protrusion may be vertical, so that as the annular protrusion wears, the area of ​​influence provided by the annular protrusion on the substrate 10 does not change. The radial location of the protrusion and the width of the protrusion may be selected based on empirically determined non-uniformity measurements for a particular polishing process.

[0030] However, many other configurations are possible for the outer abrasive surface 54. For example, the outer abrasive surface 54 may be provided by cylindrical projections that are angularly spaced, e.g., equally spaced, around the axis of rotation.

[0031] The non-contact actuator 51 may be a mechanical and / or electrical device. For example, the non-contact actuator 51 may have an air cylinder 48 attached to a pivot arm 49 that can swing upward and downward to adjust the distance between the annular flange 50 and the actuator head 46, as shown in FIG. 3. Alternatively, the non-contact actuator 51 may be stationary and fixed near the polishing station 20 with the actuator head 46 having a preset distance between the annular flange 50 and the actuator head 46.

[0032] The non-contact actuator 51 can apply an upward force to the annular confined area 44 of the annular flange 50 without physical contact between solid parts. The annular confined area 44 is smaller than the total extent of the radial arc 53 of the protrusion across the substrate 10. Specifically, the annular confined area 44 is about 0.5 to 4 mm in width and about 20 to 50 mm in length. The upward pressure applied by the non-contact actuator 51 can locally deflect the annular flange 50, which causes a portion of the protrusion of the annular flange 50 corresponding to the annular confined area 44 to move into contact with the substrate 10. The amplitude of the upward pressure by the non-contact actuator 51 can depend on the distance between the annular flange 50 and the actuator head 46. Alternatively, if the distance between the annular flange 50 and the actuator head 46 is fixed, the amplitude of the upward pressure depends on the force caused by the actuator head 46, which is controlled by the controller.

[0033] The upward pressure from the non-contact actuator 51 on the flange 50 can be generated by magnetic forces or by pneumatic or hydraulic forces, for example by an actuator head injecting fluid or air against the underside of the flange 50. The magnetic forces can be generated between two permanent magnets or between one permanent magnet and one electromagnet. The magnetic forces can repel each other, exerting an upward pressure on the annular flange 50. A detailed description of the non-contact actuator 51 is provided below.

[0034] The carrier head 70 is movable to selectively position a portion of the substrate 10 on the outer polishing pad 56. Specifically, the carrier head 70 can place a first portion of the substrate 10 on the primary polishing pad 30 and position a second portion of the substrate on the outer polishing pad 56. By selecting the position of the carrier head 70 (and thus the substrate 10) taking into account the shape and position of the outer polishing surface 54, and by controlling the degree of deformation of the flange 50 by the non-contact actuator 51, the polishing system 10 can establish a difference in polishing rate in different annular zones on the substrate. This effect can be used to perform polishing correction of the substrate 10, such as edge correction.

[0035] The carrier head 70 may rotate to provide an angularly symmetric edge modification (i.e., symmetric about the axis of rotation of the carrier head and therefore about the center of the substrate). However, in some implementations, the carrier head 70 does not rotate during the polishing modification provided by the outer polishing pad 56. This allows the correction polishing to be performed in an angularly asymmetric manner.

[0036] The polishing system 20 may have a second annular flange 60 that projects radially inward from the platen 24 into the aperture 26. When not deflected or deformed, the upper surface of the second annular flange 60 is flush with the upper surface 38 of the platen 24. The second annular flange 60 has an outer edge that is fixed to the platen 24 and rotatable therewith, and an inner edge of the second annular flange 60 is fixed relative to the upper surface of the platen 24. The second annular flange 60 may be vertically deflectable such that the inner edge of the annular flange 60 is vertically movable relative to the outer edge when the second non-contact actuator 61 applies pressure to the underside of the annular flange 60 in the angularly limited region 44. The second non-contact actuator 61 may, for example, have an air cylinder 48 attached to a pivot arm 49 that can swing upward and downward to adjust the distance between the second annular flange 60 and the actuator head 46. Alternatively, the second non-contact actuator 61 may be stationary and fixed near the polishing station 20 with the actuator head 46 having a preset distance between the second annular flange 60 and the actuator head 46.

[0037] Carrier head 70 may be movable to selectively position portions of substrate 10 over primary polishing pad 30 and inner polishing pad 66. If platen 24 includes apertures 26, carrier head 70 may be positioned laterally such that substrate 10 extends partially through holes 31 in primary polishing pad 30 during polishing.

[0038] By replacing the central region of the primary polishing pad 30 with holes 31, the polishing system 20 can reduce the in-plane non-uniformity without compromising throughput. To understand this, the polishing rate near the center of the primary pad 30 may have a reduced polishing rate compared to the more outer portions of the primary pad 30 (see FIG. 2) because the speed of the pad increases proportionally as a function of the radial distance r from the axis of rotation 25. Thus, portions of the primary pad 30 with smaller values ​​of r will have lower speeds and slower polishing rates. Thus, by replacing the less efficient central portion of the primary pad 30 with an inner polishing pad 66 configured for polishing edge control, optimal polishing quality can be obtained while maintaining at least the original throughput.

[0039] The polishing system 20 may include an inner polishing pad 66 supported by and secured to the second annular flange 60. The inner polishing pad 66 may be angularly segmented. The angular segmentation of the inner polishing pad 66 may be achieved by channels 67. The channels 67 may also be used to drain polishing by-products, such as slurry or debris from polishing.

[0040] The polishing surface 64 of the inner polishing pad 66 may be annular. In some implementations, the inner polishing pad 66 includes an annular ridge extending upward from the lower layer. The channels 67 may divide the annular ridge into a number of arcs. The upper surface of the annular ridge provides the inner polishing surface 64. The annular ridge has a width w. The width w may be angularly uniform around the circumference of the platen. The annular ridge may have a rectangular cross-section (perpendicular to the upper surface of the second annular flange 60 or the polishing surface 36).

[0041] Because only one segmented pad can be positioned under the substrate 10 at a time, the inner and / or outer pads that are not under the carrier head 70 can be conditioned by the conditioning system 40 while rotating about the axis of rotation 25 of the platen 24.

[0042] The polishing surface of the inner polishing pad 66 may be annular such that it is supported by and secured to an upper portion of the second annular flange 60. The carrier head 70 may hold the substrate 10 in contact with the primary polishing pad 30 and is movable to selectively position portions of the substrate 10 over the primary polishing pad 30 and the inner polishing pad 66 to perform modification, such as edge modification, of the substrate 10.

[0043] The polishing system 20 may have an outer polishing pad 56 that is harder than the primary polishing pad 30 or softer than the primary polishing pad 30. The outer polishing pad 56 may be constructed of the same material as the primary polishing pad 30 or may be constructed of a different material than the primary polishing pad 30.

[0044] The polishing system 20 may have an inner polishing pad 66 that is harder than the primary polishing pad 30 or softer than the primary polishing pad 30. The inner polishing pad 66 may be constructed of the same material as the primary polishing pad 30 or may be constructed of a different material than the primary polishing pad 30.

[0045] The polishing system 20 may have an outer polishing pad 56 that is harder than the inner polishing pad 66 or that is softer than the inner polishing pad 66. The outer polishing pad 56 may be constructed of the same material as the inner polishing pad 66 or may be constructed of a different material than the inner polishing pad 66.

[0046] Returning to FIG. 3, the non-contact actuator 51 may include a magnetic actuator head 46 (see FIGS. 4 and 5), a fluid jet actuator (see FIG. 6) or an air jet actuator (see FIG. 7).

[0047] 4 and 5, for implementations involving magnetic actuation, the annular flange 50 includes a permanent magnet. The permanent magnet may be affixed to an outer portion of the annular flange 50 and / or an inner portion of the annular flange 60. The magnetic actuator head may include another permanent magnet or an electromagnet. To apply an upward pressure to the annular flange 50 or 60, a permanent magnet affixed to the annular flange and a permanent magnet or an electromagnet affixed to the actuator head must be positioned opposite each other to generate a repulsive force between the annular flange and the actuator head. The amplitude of the repulsive force, or the upward pressure on the annular flange, increases nonlinearly as the distance between the annular flange and the actuator head decreases.

[0048] 4 is a schematic cross-sectional view of an example of a chemical mechanical polishing system with a non-contact actuator having a permanent magnet. As shown in FIG. 4, a permanent magnet 420 is fixed to the flange 50, for example embedded inside the flange 50. Alternatively, the permanent magnet 420 can be fixed to an outer surface of the annular flange 50, for example the bottom surface of the annular flange 50. The permanent magnet 420 has two poles, a lower north pole 407 and a south pole 409.

[0049] The magnetic actuator 51 includes a magnetic actuator head 46. A separate permanent magnet 410 is affixed to the magnetic actuator head 46, for example embedded in the actuator head 46. Alternatively, the permanent magnet 410 may be affixed to an outer surface of the actuator head 46, for example the top surface of the actuator head 46. The permanent magnet 410 has two poles, a north pole 403 and a south pole.

[0050] The two permanent magnets 410 and 420 are positioned such that like poles of the two permanent magnets 410 and 420 face each other. For example, the north pole 407 of the magnet 420 faces the north pole 403 of the magnet 410, as shown in FIG.

[0051] The shape of the permanent magnets 420 may be a ring, such as the outer polishing pad 56, or multiple radial arcs, such as the radial arc 53. Each magnet arc may share a width that is the same as or less than the width w (measured along the radius of the platen) of the radial arc 53. The width w may be uniform for each magnet arc. Each arc may have the same dimensions, or the width w may vary from magnet arc to magnet arc. The total number of permanent magnets 420 secured to the annular flange may be one or more. Similarly, the total number of permanent magnets 410 secured to the magnetic actuator head may be one or more. For example, the number of permanent magnets 420 may be eight, while the number of permanent magnets 410 may be two.

[0052] The repulsive force generated by the permanent magnets 410 and 420 generally depends on the distance of the gap 405 between the annular flange 50 and the actuator head 46, or more precisely, the distance between the magnets 420, 410 and the relative orientation of the magnets 420, 410. If no magnetic force is required between the actuator head 46 and the flange 50, the actuator head 46 can be positioned away from the flange 50. There is no specific maximum distance, but the head may be at least 3 mm from the flange 50. On the other hand, if the polishing apparatus controller determines that an increase in pressure is required to be applied to the platen edge, the actuator head 46 is moved closer to the flange to substantially deform the flange with the upward magnetic force. In this case, the gap 405 is narrower, but may be at least 1 mm wide. The amplitude of the repulsive force, or equivalently, the upward pressure applied to the annular flange 50, may vary nonlinearly as the distance of the gap 405 changes.

[0053] To adjust the force on the flange, the actuator 51 may have an arm 49 attached to an air cylinder 48. The arm 49 may move the actuator 46 upward and downward based on the movement of the air cylinder. The distance of the gap 405 may be determined and adjusted by a controller to apply an appropriate upward pressure on the annular flange. The annular flange 50 may be deflected upward to press the polishing pad 56 onto the substrate 10 to control the polishing rate of the edge of the substrate. The deflection of the annular flange may be 1 mm to 3 mm to ensure contact between the polishing pad 56 and the substrate 10 with extra external pressure.

[0054] As shown in FIG. 4, a plurality of bolts 81, 82 can be used to fasten the flange 50 to the platen 24. Furthermore, a first plurality of bolts 81 is screwed vertically or diagonally into the base of the platen, and a second plurality of bolts 82 is screwed horizontally into the base of the platen. The bolts 81, 82 can be used to adjust the surface height of the primary polishing pad 30 and at the same time adjust the size of the gap 55. For example, slots 421, 422 can be formed in the base of the flange 50, and the bolts 81, 82 can be inserted through the slots. The vertical and horizontal positions of the flange 50 can be set by sliding the base of the flange 50 along the bottom of the platen 24 before tightening the bolts 81, 82. Using a combination of the bolts 81 and 82, the surface height of the primary polishing pad 30 can be adjusted to be substantially flush with the surface of the outer polishing pad 56, and the size of the gap 55 can be adjusted accordingly.

[0055] Similar to FIG. 4, FIG. 5 is a schematic cross-sectional view of an example of a chemical mechanical polishing system with a non-contact actuator having an electromagnet. The annular flange 50 has a permanent magnet 520. The electromagnet 510 is fixed to the magnetic actuator head, for example, embedded inside the magnetic actuator head 46. Alternatively, the electromagnet 510 may be located on the outer surface, for example, the top surface, of the magnetic actuator head 46. The electromagnet 510 includes a coil 503 that optionally surrounds a low magnetic permeability core 501. The coil 503 is connected to a controller 510. The controller 510 can determine a change in current flowing through the coil 503 to control the electromagnetic field strength and polarity of the electromagnet 510. As shown in FIG. 5, the controller 510 can determine a voltage source to apply a current to the electromagnet 510 such that the electromagnet generates a non-zero magnetic field with the same poles of the permanent magnet 520 and the electromagnet 510 facing each other. For example, as shown in FIG. 5, the south pole 507 of the permanent magnet 520 faces towards the south pole of the electromagnet 510 .

[0056] 4, the shape of the permanent magnets 420 may be a ring, such as the outer polishing pad 56, or a number of radial arcs, such as the radial arc 53. The total number of permanent magnets 520 secured to the annular flange may be one or more. Similarly, the total number of electromagnets 510 secured to the magnetic actuator head 46 may be one or more. For example, the number of permanent magnets 520 may be twelve, while the number of electromagnets 510 may be three.

[0057] Similarly, the repulsive force generated between the permanent magnet 520 and the electromagnet 510 generally depends on the size of the gap 505 between the annular flange 50 and the actuator head 46, or more precisely, the distance and relative orientation between the permanent magnet 520 and the electromagnet 510. The amplitude of the repulsive force, or equivalently, the upward pressure applied to the annular flange 50, may vary linearly as the electromagnetic field strength of the electromagnet 510 controlled by the controller 510 varies. In some implementations, the actuator 51 may be fixed at a position having a preset initial size of the gap 505. The annular flange 50 may be deflected upward to press the polishing pad 56 onto the substrate 10. The total amount of deflection of the annular flange depends on the electromagnetic field strength of the electromagnet 510 when the actuator is fixed at that position. The electromagnetic field strength may be controlled according to an in-situ polishing control system that measures the polishing process of the substrate in real time. The controller 510 can take the polishing process as input and adjust the current rate and amplitude accordingly to increase or decrease the electromagnetic field strength of the electromagnet 510. The deflection of the annular flange can be 1 to 3 mm to ensure positive contact pressure between the polishing pad 56 and the substrate 10.

[0058] Alternatively, the non-contact actuator 51 may include a fluid jet actuator head. The fluid jet actuator head includes a fluid nozzle connected through a pipe to a fluid source. The fluid source may include a fluid such as water. A valve may be incorporated between the fluid source and the fluid nozzle to turn on and off the fluid from the fluid source to the fluid nozzle. The fluid jet actuator head is configured to eject fluid from the nozzle onto the annular flange when the valve is turned on.

[0059] FIG. 6 is a schematic cross-sectional view showing an example of a chemical mechanical polishing system with a non-contact actuator having a fluid jet nozzle. The non-contact actuator 51 includes a fluid jet actuator head 46. The fluid jet actuator head 46 includes a fluid nozzle 601 positioned on an outer surface, e.g., an upper surface, of the actuator head 46. The fluid nozzle 601 is connected to one end of a fluid valve 605 via a conduit 603, e.g., a tubing or flexible tube. The other end of the fluid valve 605 is connected to a fluid source 610. The fluid valve 605 is also connected to a controller 620 by a signal line 607, and the controller 620 can send a signal through the signal line 607 to turn the valve 605 on or off. When the valve 605 is off, no fluid is ejected from the nozzle 601 because the fluid pressure from the fluid source 610 cannot reach the fluid in the pipe 603. However, when valve 605 is turned on, fluid from fluid source 610, for example by a pump or back pressure, flows through nozzle 601 and is sprayed onto the bottom surface of annular flange 50. Valve 605 may be partially turned on by controller 620 to control the flow rate of the fluid. The fluid may be a gas, such as air or nitrogen, or a liquid, such as water. In either case, the fluid may be filtered before flowing through the nozzle.

[0060] The upward pressure applied to the annular flange is determined by the linear momentum carried by the fluid ejecting through the fluid nozzle 601. The higher the flow rate, the stronger the upward pressure on the annular flange 50. In some implementations, the nozzle 610 can also control the flow rate to increase and decrease the pressure applied to the annular flange. The upward pressure can deflect the annular flange upward and into contact with the substrate 10 during polishing edge control, ultimately applying more pressure to the substrate.

[0061] The controller 620 can be connected to an in situ monitor system that can measure the polishing progress on the substrate being polished in real time and determine a signal to send to the valve through signal line 607 to adjust how much to turn on the valve 605. In some implementations, the valve 605 does not have an intermediate state between a switched on state and an off state. However, the fluid source can be connected to a fluid pump that can vary the fluid pressure of the fluid source controlled by the controller through a pressure line.

[0062] In some implementations, the size of gap 605 may affect the upward pressure applied to annular flange 50 because a larger gap may result in a less focused jet of fluid onto the bottom surface of annular flange 50, reducing the upward pressure. Typically, gap 605 is preset small, e.g., 1-3 mm, so that the effect of the size of gap 605 is substantially negligible, especially when the fluid pressure of fluid source 610 is much higher than normal atmospheric pressure.

[0063] Alternatively, the non-contact actuator 51 may include an air jet actuator head. The air jet actuator head includes an air nozzle connected through a pipe to a compressed air source. The compressed air source may include an inert gas such as nitrogen. A valve may be incorporated between the compressed air source and the air nozzle for turning on and off the connection between the compressed air source and the air nozzle. The air jet actuator head is configured to inject air from the nozzle onto the annular flange when the valve is turned on.

[0064] The total number of fluid sources 610 can be one or more. For example, the total number of fluid sources 610 can be five. Each fluid source 610 can have a respective pressure or pressures independently controlled by a respective controller. The valve 605 can be a multi-threaded valve with the other end of the valve connected to multiple fluid sources. Alternatively, the non-contact actuator 51 can have multiple valves, each connected to a respective fluid source 610 and independently controlled by the controller 190.

[0065] The term substrate as used herein may include, for example, a product substrate (e.g., containing multiple memory or processor dies), a test substrate, a bare substrate, and a gate substrate. The substrate may be at various stages of integrated circuit manufacturing, for example, the substrate may be a bare wafer or may include one or more deposited and / or patterned layers. The term substrate may include a circular disk and a rectangular sheet.

[0066] The polishing system and method described above can be applied to a variety of 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 fillers), soft material, or fixed abrasive material. Although the term relative positioning is used, it should be understood that the polishing surface and the substrate can be held in a vertical orientation or any other orientation.

[0067] Although specific embodiments of the present invention have been described, other embodiments are within the scope of the following claims. For example, the steps recited in the claims can be performed in a different order and still achieve desirable results.

Claims

1. 1. A polishing system comprising: a platen having an upper surface supporting a primary polishing pad, the platen being rotatable about an axis of rotation passing substantially through a center of the platen; an annular flange disposed radially outward of the platen, the annular flange having an upper surface for supporting an outer polishing pad, the annular flange being secured to the platen and rotatable therewith, an inner edge of the annular flange being secured to or disposed against an outer edge of the platen, the annular flange being deflectable upwardly such that the outer edge of the annular flange is higher than the inner edge of the annular flange; a non-contact actuator configured to apply pressure to a lower surface of the annular flange in a region that is limited to a portion of an arc about the axis of rotation without contacting the annular flange; a carrier head that holds a substrate in contact with the primary polishing pad and is movable to selectively position a portion of the substrate on the outer polishing pad; A polishing system comprising:

2. The polishing system of claim 1 , wherein the non-contact actuator comprises a magnetic actuator head.

3. The polishing system of claim 2, wherein the annular flange includes a first permanent magnet fixed to an outer portion of the annular flange, and the magnetic actuator head includes a second permanent magnet positioned opposite the first permanent magnet in a non-contact manner so that one pole of the first permanent magnet faces toward a same pole of the second permanent magnet.

4. The polishing system of claim 2, wherein the annular flange includes a first permanent magnet fixed to an outer portion of the annular flange, and the magnetic actuator head includes an electromagnet positioned opposite the first permanent magnet in a non-contact manner so that one pole generated by the electromagnet faces toward the same pole of the first permanent magnet.

5. The polishing system of claim 1 , wherein the non-contact actuator comprises a fluid jet actuator head.

6. The polishing system of claim 5 , wherein the fluid jet actuator head includes a nozzle connected to a fluid source, the fluid jet actuator head configured to jet fluid to apply pressure to the underside of the annular flange.

7. The polishing system of claim 1 , wherein the non-contact actuator comprises an air jet actuator head.

8. The polishing system of claim 7 , wherein the air jet actuator head includes a nozzle connected to a source of compressed air, the air jet actuator head configured to jet air to apply pressure to the underside of the annular flange.

9. The polishing system further comprises: an aperture in the top surface of the platen approximately at the center of the platen; a second annular flange disposed within the aperture radially inward of the platen, the second annular flange having an upper surface that supports an inner polishing pad, the second annular flange being secured to the platen and rotatable therewith, an outer edge of the second annular flange being secured to or disposed against an inner edge of the platen, the second annular flange being deflectable upwardly such that the inner edge of the second annular flange is higher than the outer edge of the second annular flange; a second non-contact actuator configured to apply pressure to a lower surface of the second annular flange in a region that is limited to a portion of an arc about the axis of rotation without contacting the second annular flange; The polishing system of claim 1 .

10. The polishing system of claim 9 , wherein the second non-contact actuator comprises a magnetic actuator head.

11. A polishing system as described in claim 10, wherein the second annular flange includes a first permanent magnet fixed to an inner portion of the second annular flange, and the magnetic actuator head includes a second permanent magnet positioned opposite the first permanent magnet in a non-contact manner so that one pole of the first permanent magnet faces toward a same pole of the second permanent magnet.

12. The polishing system of claim 10, wherein the second annular flange includes a first permanent magnet fixed to an inner portion of the second annular flange, and the magnetic actuator head includes an electromagnet positioned opposite the first permanent magnet in a non-contact manner so that one pole generated by the electromagnet faces toward the same pole of the first permanent magnet.

13. The polishing system of claim 9 , wherein the second non-contact actuator comprises a fluid jet actuator head.

14. 14. The polishing system of claim 13, wherein the fluid jet actuator head includes a nozzle connected to a fluid source, the fluid jet actuator head configured to jet fluid to apply pressure to the underside of the second annular flange.

15. The polishing system of claim 9 , wherein the second non-contact actuator comprises an air jet actuator head.

16. 16. The polishing system of claim 15, wherein the air jet actuator head includes a nozzle connected to a source of compressed air, the air jet actuator head configured to jet air to apply pressure to the underside of the second annular flange.

17. The polishing system of claim 1 , wherein a top surface of the annular flange is flush with a top surface of the platen.

18. 1. A polishing system comprising: an annular platen having a top surface for supporting a primary polishing pad, the annular platen having an aperture in the top surface of the platen approximately at a center of the platen and rotatable about an axis of rotation passing approximately through the center of the platen; an annular flange disposed within the aperture radially inward of the platen, the annular flange having an upper surface that supports an inner polishing pad, the annular flange being secured to the platen and rotatable therewith, an outer edge of the annular flange being secured to or disposed against an inner edge of the platen, the annular flange being deflectable upwardly such that the inner edge of the annular flange is higher than the outer edge of the annular flange; a non-contact actuator configured to apply pressure to a lower surface of the annular flange in a region that is limited to a portion of an arc about the axis of rotation without contacting the annular flange; a carrier head that holds a substrate in contact with the primary polishing pad and is movable to selectively position a portion of the substrate on the inner polishing pad; A polishing system comprising:

19. 20. The polishing system of claim 18, wherein the non-contact actuator includes a magnetic actuator head, a first permanent magnet fixed to an inner portion of the annular flange, and a second permanent magnet positioned opposite the first permanent magnet in a non-contact manner such that one pole of the first permanent magnet faces toward a same pole of the second permanent magnet.

20. 20. The polishing system of claim 18, wherein the non-contact actuator includes a magnetic actuator head, a first permanent magnet is fixed to an inner portion of the annular flange, and the magnetic actuator head includes an electromagnet positioned in a non-contact opposing relationship to the first permanent magnet such that one pole generated by the electromagnet faces toward the same pole of the first permanent magnet.

Images