Roller for location-specific wafer polishing.

Abstract

The polishing apparatus includes a support configured to receive and hold a substrate in a plane, a polishing pad affixed to a cylindrical surface of a rotary drum, a first actuator for rotating the drum about a first axis parallel to the plane, a second actuator for bringing the polishing pad on the rotary drum into contact with the substrate, and a port for dispensing a polishing liquid to an interface between the polishing pad and the substrate.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to chemical mechanical polishing, and more particularly to the use of rollers to address polishing non-uniformities. [Background technology]

[0002] Integrated circuits are typically formed on a substrate (eg, a semiconductor wafer) by the sequential deposition of conductive, semiconductive, or insulating layers onto the silicon wafer and subsequent processing of said layers.

[0003] One manufacturing step involves depositing a filler layer over a non-planar surface and planarizing the filler layer until the non-planar surface is exposed. For example, a conductive filler layer may be deposited on a patterned insulating layer to fill trenches or holes in the insulating layer. The filler layer is then polished until the raised patterns of the insulating layer are exposed. 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. Additionally, planarization may be used to planarize the substrate surface for lithography.

[0004] Chemical-mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that a substrate be mounted on a carrier head. The exposed surface of the substrate is placed against a rotating polishing pad. The carrier head applies a controllable load to the substrate to press it against the polishing pad. A polishing fluid, such as a slurry having abrasive particles, is supplied to the surface of the polishing pad during material removal. Summary of the Invention

[0005] In one embodiment, a polishing apparatus includes a support configured to receive and hold a substrate in a plane, a polishing pad affixed to the cylindrical surface of a rotary drum, a first actuator for rotating the drum about a first axis parallel to the plane, a second actuator for bringing the polishing pad on the rotary drum into contact with the substrate, and a port for dispensing a polishing liquid to the interface between the polishing pad and the substrate.

[0006] In another aspect, a method for chemically mechanically polishing a substrate includes contacting a cylindrical polishing surface of a roller with a front surface of the substrate with a major axis of the roller parallel to the polishing surface, supplying a polishing liquid to an interface between the polishing pad and the substrate, and causing relative motion between the roller and the substrate to polish under-polished areas of the substrate without removing material from at least a portion of the front surface of the substrate, wherein the relative motion includes at least rotating the roller about the major axis while pressing the roller against the front surface of the substrate.

[0007] In another aspect, a method of chemically mechanically polishing a substrate includes obtaining a thickness profile of the substrate, determining angular asymmetry in polishing of the substrate from the thickness profile, contacting a cylindrical polishing surface of a roller with a front surface of the substrate with a major axis of the roller parallel to the polishing surface, supplying a polishing liquid to the surface of the substrate, rotating the roller about the major axis while pressing the roller against the front surface of the substrate, and at least one of decreasing a rotational speed of the substrate, increasing a rotational speed of the roller, or increasing a pressure of the roller against the front surface of the substrate as an under-polished region of the substrate passes under the roller to compensate for the angular asymmetry.

[0008] In another aspect, a method for chemically mechanically polishing a substrate includes contacting a cylindrical polishing surface of a roller with a front surface of a substrate with a major axis of the roller parallel to the polishing surface, supplying a polishing liquid to the surface of the substrate, and rotating the roller about the major axis while pressing the roller against the front surface of the substrate.

[0009] Advantages of embodiments may include, but are not limited to, one or more of the following.

[0010] By using location-specific profile correction with a polishing roller, within-wafer non-uniformity (WIWNU) and between-wafer non-uniformity (WTWNU) can be reduced. Material removal can compensate for edge thickness non-uniformity induced after the main CMP step and / or correct the incoming substrate film thickness profile before undergoing main polishing. With location-specific polishing, the pressure applied by the polishing roller is transferred directly to the substrate surface rather than through the wafer backside, increasing location specificity and reducing substrate deflection. The dimensions of the pressure zone are small and controlled by the dimensions of the polishing roller, allowing material removal within a very specific area.

[0011] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic perspective view of a substrate polishing apparatus. [Figure 2A] 2A and 2B are schematic side views of an exemplary substrate polishing apparatus including one or two rotary polishing pads. [Figure 2B] 2A and 2B are schematic side views of an exemplary substrate polishing apparatus including one or two rotary polishing pads. [Figure 3] 1 is a chart showing an example of an edge thickness profile. [Figure 4] 1 is a chart depicting a first edge thickness profile before treatment and a second edge thickness profile following treatment. [Figure 5A] 5A and 5B are schematic top views of the substrate polishing apparatus. [Figure 5B] 5A and 5B are schematic top views of the substrate polishing apparatus. [Figure 6A] 6A-6C are schematic diagrams of a substrate polishing apparatus including a wheel-shaped polishing pad. [Figure 6B] 6A-6C are schematic diagrams of a substrate polishing apparatus including a wheel-shaped polishing pad. [Figure 6C] 6A-6C are schematic diagrams of a substrate polishing apparatus including a wheel-shaped polishing pad. DETAILED DESCRIPTION OF THE INVENTION

[0013] Like reference numbers and designations in the various drawings indicate like elements.

[0014] During CMP processing, the substrate thickness across the surface of the substrate can vary due to inconsistent polishing pad or carrier head pressure, dwell time, and other inherent polishing non-uniformities. For example, some substrates are prone to "checkmark" non-uniformities, where an annular region near but not at the edge of the substrate is under-polished. In addition, the substrate edge can be prone to asymmetry.

[0015] CMP processing vendors impose strict film thickness uniformity thresholds on deliverable substrates. Typical CMP processes often achieve these thresholds over most of the substrate's central surface area. However, interactions between the substrate edge, the polishing pad, and the head retaining ring result in non-uniformities within the edge region, including "checkmark" features that cannot be eliminated by head zone pressure control. Furthermore, incoming substrates may contain non-uniform film thickness profiles, such as large pre-existing edge thickness profiles, that are challenging or impossible to correct using existing head technology.

[0016] For example, various "touch-up" polishing processes have been proposed that use small rotating disk-shaped polishing pads, but such "touch-up" polishing processes contact the substrate over a small area and therefore have low throughput.

[0017] Described herein is a location-specific polishing method. The method can provide substrate edge thickness profile correction. Material removal is performed by a polishing roller, e.g., a polishing pad attached to the outer surface of a cylindrical roller. The parameters of the polishing roller, e.g., roller diameter and pad grit, can be selected to correspond to the substrate shape and / or thickness profile, providing design flexibility. In addition, the polishing roller can be purchased conventionally or 3D printed, thereby realizing cost savings and reducing device downtime for maintenance. A controller functions to optimize the substrate rotation speed, polishing roller rotation speed, and roller scanning profile to achieve precise location-specific material removal.

[0018] FIG. 1 illustrates an example chemical mechanical polishing apparatus 100 for polishing underpolished areas of a substrate. The polishing apparatus 100 includes a rotatable, disk-shaped platen 110 on which the substrate 10 rests. The platen 110 is operable to rotate about a first axis 114, e.g., a motor can turn a drive shaft to rotate the platen 110. The substrate 10 is held on the upper surface of the platen 110 by a vacuum source 112, e.g., a vacuum applied to the bottom surface of the substrate 10 by a vacuum chuck. The vacuum platen 110 maintains the orientation and position of the substrate 10 on the platen 110 as it rotates about the axis 114. The vacuum platen 110 presents the entire top surface of the substrate 10 to the polishing apparatus 100 and does not interfere with the polishing process.

[0019] The polishing apparatus 100 includes a first actuator that operates to rotate a rotary drum 118 about a main axis. A polishing pad 119 is attached to at least a portion of the cylindrical outer surface of the drum 118, thus forming a cylindrical polishing surface. The drum 118 and the attached polishing pad 119 constitute a roller 120. The polishing surface of the roller 120 is made of a material suitable for polishing and planarizing the substrate 10. The polishing pad material may be a polymer layer, such as polyurethane, or a microporous layer, such as IC1000™ polishing layer material. The drum 118 in FIG. 1 is cylindrical with a length greater than its diameter. It may be cylindrical with a length less than its diameter. The major axis of rotation is coaxial with the longitudinal axis of roller 120. Roller 120 is positioned so that the major axis is parallel to the front, e.g., upper, surface of substrate 10.

[0020] The polishing apparatus 100 includes a second actuator for controlling the vertical position of the roller 120 relative to the substrate 10 and the platen 110. The second actuator operates to bring the longitudinal surface of the roller 120 into contact with the surface of the substrate 10 and to move the surface of the roller 120 away from the surface of the substrate 10.

[0021] Polishing apparatus 100 includes a port 130 for dispensing a polishing fluid 132, such as an abrasive slurry, onto roller 120. Alternatively, the port may dispense the polishing fluid directly onto substrate 10, where it will be carried by rotation of platen 110 below roller 120.

[0022] Polishing apparatus 100 may also include a polishing pad conditioner 140, such as a diamond-embedded conditioner disk, for polishing the surface of roller 120 to maintain a consistent polishing condition of roller 120. Pad conditioner 140 may be placed adjacent to platen 110 in a surface-up position that is approximately flush with the top of platen 110 or substrate 10.

[0023] 2A and 2B illustrate the operation of polishing apparatus 100 utilizing one roller 120 and two rollers 220, e.g., roller 220a and roller 220b, respectively. Referring to FIG. 2A, platen 110 supporting substrate 10 rotates about axis 114. Roller 120 is rotated about a primary axis, such as by a second motor controlling the rotational movement of roller 120. In the side view of FIG. 2A, the primary axis extends into the page.

[0024] Polishing liquid 132 is supplied to the polishing surface of roller 120 through port 130, as shown in Figure 1. In some embodiments, polishing liquid 132 is supplied to the surface of substrate 10 through port 130. The major axis of roller 120 can be oriented at any angle ranging from 0° (e.g., parallel) to 90° (e.g., perpendicular) with respect to a line (e.g., a line segment) connecting the center point of substrate 10 to the center point of roller 120. For example, the major axis of roller 120 in Figure 1 is oriented perpendicular (e.g., at 90°) to the line connecting the center point of substrate 10 to the center point of roller 120.

[0025] Referring to FIG. 5A , because areas of the top surface near the substrate edge are often underpolished, a particularly useful embodiment is one in which the edge 122 of the roller 120 is positioned at or near, e.g., within 2 mm, the edge 12 of the substrate 10. In addition, the roller 120 is substantially perpendicular (e.g., 80-90° from) to a line R connecting the center point 14 of the substrate to the center point 124 of the roller. In this configuration, the polishing action is concentrated in an annular region 20 of the top surface of the substrate 10 adjacent the substrate edge 12, at a higher polishing rate than in regions 22 away from the substrate edge. A central region 24 radially inward of the annular region 20 is not polished. This configuration is particularly well suited for correcting the checkmark region. Note that polishing here occurs on the generally flat surface of the substrate.

[0026] Alternatively, as shown in FIG. 5B , the edge 122 of the roller 120 may be positioned radially inward from the edge 12 of the substrate 10, e.g., 1 to 30 mm. Again, the roller 120 is substantially perpendicular (e.g., 80 to 90 degrees from) to a line R connecting the center point 14 of the substrate to the center point 124 of the roller. In this configuration, the polishing action is concentrated at an annular region 30 on the upper surface of the substrate 10, away from the substrate edge 12. The polishing rate may be higher in a region 32 near the inner diameter of the annular region 30. A central region 34 radially inward of the annular region 30 and a second annular region 36 surrounding the polished annular region 30 are not polished. This configuration may also be well suited to checkmark region correction.

[0027] 1, roller 120 contacts the front surface of substrate 10 to create a contact area between the polishing surface of roller 120 and the front surface of substrate 10. Polishing apparatus 100 commands the second actuator to apply a force, e.g., push, roller 120 toward the substrate in a direction perpendicular to substrate 10, e.g., downward in FIG. 2A. The force applied to the contact area via roller 120 may range from 30 psi to 70 psi (e.g., 40 psi to 50 psi, or 60 psi to 70 psi).

[0028] The rotational motion of the polishing surface of roller 120 in the presence of polishing liquid 132 removes, e.g., polishes, a portion of substrate 10 material within the contact area, while not removing substrate 10 material outside the contact area. If necessary, roller 120 can be moved along an axis parallel to the plane of substrate 10, e.g., from right to left in FIG. 2A , to vary the position of the contact area along the front surface of substrate 10. The rotation of substrate 10 and the rotational and translational motion of roller 120 create relative motion between roller 120 and the front surface of substrate 10. While in contact with substrate 10, the rotational speed of roller 120 can range from 10 rpm to 2500 rpm (e.g., 50 rpm to 1500 rpm).

[0029] The period of time that the roller 120 polishing surface is in contact with the substrate 10 is the contact time. The residence time of the roller over any particular area, along with the pressure and rotational speed, determines the amount of material removed from the substrate. After the contact time between the roller 120 and the substrate 10 polishing surface, the roller 120 may be removed from the substrate 10 to stop polishing. The contact time may range from less than 1 second to 600 seconds.

[0030] After the polishing operation is completed, the polishing surface can be reconditioned by removing roller 120 from in front of substrate 10 and contacting the polishing surface of roller 120 with pad conditioner 140. For example, a second actuator moves the roller horizontally from a position above the substrate to a position above pad conditioner 140. Polishing apparatus 100 rotates roller 120 while in contact with pad conditioner 140, thereby scraping off the outer layer of the polishing surface of roller 120. Roller 120 remains in contact with pad conditioner 140 while continuing to rotate for the conditioning period. In some embodiments, further relative motion between roller 120 and pad conditioner 140 can include translating roller 120 along an axis parallel to the surface of pad conditioner 140.

[0031] 2B illustrates another embodiment of a polishing apparatus 200 including rollers 220a and 220b (collectively, rollers 220) for polishing a substrate 10. The substrate 10 rotates on a platen 110 about an axis 114. Two ports, 230a and 230b (collectively, ports 230), are located adjacent to rollers 220a and 220b, respectively, and supply polishing liquid 132 to each. In such an embodiment, rollers 220 may be substantially the same or different, including their length, diameter, compressibility, elasticity, and material composition of their polishing surfaces. For example, the polishing surface of roller 220a may have a first durometer value, and the polishing surface of roller 220b may have a different, second durometer value.

[0032] Rollers 220a and 220b (collectively rollers 220) can have substantially the same or different relative motion between substrate 10 and each roller 220a and 220b, including their respective rotational and / or translational speeds, translational axis orientations and / or major axis orientations.

[0033] Polishing apparatus 200 includes two pad conditioners 240, pad conditioners 240a and 240b. Pad conditioners 240 may be made of substantially the same material or may be different, and may have substantially the same polishing ability (e.g., grit) or may have different polishing capabilities. For example, the conditioning surface of roller pad conditioner 240a may have a first durometer value, and the conditioning surface of roller pad conditioner 240b may have a different second durometer value. Roller 220 may be operated to contact pad conditioners 240 simultaneously or at different times.

[0034] Embodiments including two or more rollers 220 can reduce the time required to polish a substrate 10, thereby reducing the material and time costs associated with polishing a substrate 10.

[0035] The contact time, the rotational and translational speeds of the roller 120, and the pressure parameters can be determined based on the amount of material to be removed to achieve the thickness profile limit and to construct a compensation profile. The compensation profile can be loaded into the controller of the polishing apparatus 100 to control the flow rates of the platen 110, roller 120, and 132. FIG. 3 is a chart comparing the material removed from the surface of the substrate 10 on the y-axis against the wafer radial position on the x-axis. The y-axis depicts a range of removed material from 0 angstroms (Å) to 240 Å. A higher y-axis value indicates more material is removed from the surface of the substrate 10 at the corresponding x-axis radial position. The x-axis includes radial positions ranging from 120 mm to 150 mm. FIG. 3 includes lines depicting two surface profiles, a first surface profile 320a and a second surface profile 320b, extending from 120 mm to 145 mm on the x-axis.

[0036] Surface profile 320a is a calculated average profile of eight measured surface profiles as measured along eight lines extending radially from the center of substrate 10 from 120 mm to 145 mm, where the eight lines are oriented at equal radial intervals around the periphery of substrate 10.

[0037] The polishing apparatus 100 was operated to polish the substrate 10 according to two compensation profiles. The first compensation profile, corresponding to the surface profile 320a, included a pressure parameter of 45 psi, and the roller 120 was positioned at five radial positions for five respective periods of a total dwell time of 125 seconds. Along the radial lay from the center of the substrate 10, the initial roller 120 position was approximately 137 mm, the second position was approximately 135 mm, the third position was approximately 133 mm, the fourth position was approximately 131 mm, and the fifth position was approximately 128 mm.

[0038] The roller 120 had dwell times of 35 s, 30 s, 25 s, 20 s, and 15 s at the first, second, third, fourth, and fifth radial positions, respectively, after which the roller 120 withdrew from contact with the substrate 10. This created a sloped surface profile 320a in which the roller 120 removed a large amount of material at the outermost radial position (137 mm) and successively less material at the innermost radial positions.

[0039] The second correction profile, corresponding to surface profile 320b, included a pressure parameter of 45 psi, and roller 120 was positioned at four radial locations for four 15-second dwells for a total of 60 seconds. Along a radial line from the center of substrate 10, the initial roller 120 position was approximately 131 mm, the second position was approximately 133 mm, the third position was approximately 136 mm, and the fourth position was approximately 139 mm.

[0040] The roller 120 had a dwell time of 15 seconds at each radial position, after which the roller 120 withdrew from contact with the substrate 10. This created a sloped surface profile 320b in which the roller 120 removed a small amount of material at the outermost radial position (137 mm) and then removed more material at successively inward radial positions.

[0041] FIG. 4 is a chart comparing the substrate 10 surface height in angstroms measured along a line extending from the center point of the substrate 10 on the y-axis to the radial position in mm on the x-axis. FIG. 4 includes two edge profiles 420a and 420b. Edge profile 420a corresponds to the substrate 10 surface before the polishing apparatus 100 polishes the surface using the correction profile. Edge profile 420a is approximately flat at 14,500 Å between 125 mm and 135 mm on the x-axis. Between 135 mm and 150 mm, the measured substrate 10 surface corresponds to a surface height that increases to approximately 15,300 Å before decreasing to a value of approximately 14,900 Å at 149 mm on the x-axis.

[0042] Edge profile 420b shows the surface of substrate 10 after polishing apparatus 100 polishes substrate 10 according to a correction profile whose parameters are designed to correct edge profile 420a to a substantially planar surface of substrate 10. Polishing apparatus 100 achieved a substantially planar surface of substrate 10 along the measured surface, as shown in edge profile 420b.

[0043] In some embodiments, the polishing apparatus 100 includes an in-situ monitoring system for monitoring the thickness of one or more locations on the substrate. Examples of in-situ monitoring systems include optical monitoring, such as spectroscopic monitoring, eddy current monitoring, acoustic monitoring, and motor torque monitoring. The in-situ monitoring system determines the thickness, such as the thickness relative to the edge 12 or the thickness relative to the central region 24, at one or more radial positions within an annular region, such as annular region 20 or annular region 30. The polishing apparatus 100 controller constructs a thickness profile from the thickness at one or more locations. In some embodiments, the thickness profile may be determined using an in-line metrology system. Examples of in-line monitoring systems include optical monitoring, such as a color imager, a spectroscopic sensor, or an ellipsometer, or an eddy current sensor.

[0044] For example, a first thickness profile may be determined from an annular region 20 on the surface of the substrate 10. The annular region 20, with its outer radius aligned with the substrate edge 12, produces an edge thickness profile. The polishing apparatus 100 contacts the annular region 20 with a roller 120 and polishes the annular region 20 for a period of time.

[0045] The polishing apparatus 100 determines a second thickness profile (e.g., a second edge thickness profile) using an in-situ monitoring system of the annular region 20. The polishing apparatus 100 compares the first edge thickness profile to the second edge thickness profile to determine an edge thickness difference. In some embodiments, the first and second edge thickness profiles are compared, and an edge thickness difference is determined during polishing. When the edge thickness difference falls below a threshold value stored in the polishing apparatus 100, the polishing apparatus 100 causes the second actuator to not contact the polishing pad with the substrate 10 using a chart that compares the edge thickness difference.

[0046] The roller 120 can be configured to conform to different shape profiles. While the examples described above include a horizontally oriented cylindrical roller 120 throughout some embodiments, the roller 120 may also be wheel-shaped, with a radius greater than the length of the roller 120. Such an embodiment provides a lower roller 620 contact surface with the substrate 60, enhancing polishing spatial resolution.

[0047] FIG. 6A shows an example polishing apparatus 600 including a wheel-shaped roller 620 connected to a motor 650. The roller 620 contacts a substrate 60 disposed on a platen 610, which includes a vacuum source 612 for maintaining the position and orientation of the substrate 60 on the platen 610 during polishing. The polishing apparatus 600 dispenses a polishing liquid 632 onto the surface of the substrate 60 through a port 630, and the motor 650 operates to impart rotational motion to the roller 620 while in contact with the substrate 60. The polishing apparatus 600 includes a pad conditioner 640 for scrubbing and reconditioning the roller 620. As shown in FIG. 2B, the polishing apparatus 600 can include more than one roller 620 and / or more than one pad conditioner 640 for each respective roller 620.

[0048] Platen 610 rotates about a first vertical central axis, and roller 620 rotates about a second axis that is perpendicular to the first and parallel to the surface of substrate 60. In some embodiments, motor 650 can translate roller 620 along the second axis to create relative motion between substrate 60 and roller 620 in three dimensions, which can be in addition to or instead of motion along the first and second rotational axes.

[0049] 6B depicts a side view along a second rotational axis of the roller 620, which, for example, coincides with the rotational axis of the motor 650. The roller 620 includes a rigid central drum 622 around which an inflatable support tube 624 surrounds. The support tube 624 provides at least a portion of the pressure applied to the pad 626 when in contact with the substrate 60. In some embodiments, the support tube 624 is inflated to a pressure ranging from 1 psi to 50 psi. In various exemplary embodiments, the support tube 624 inflation pressure is a parameter controlled by the polishing apparatus 600 within a compensation profile to achieve an edge profile, such as the planar edge profile 420b.

[0050] 6A and 6B. Such an embodiment may be particularly useful for increasing polishing spatial resolution by reducing the contact area of ​​roller 620. Roller 620 is substantially perpendicular to (e.g., 80 to 90 degrees from) a line R connecting the center point 14 of the substrate to the center point 625 of the roller.

[0051] 5A and 5B are cylindrical and oriented with their lengths parallel to the surface of substrate 10, resulting in a high surface area of ​​contact, whereas roller 620 is a wheel oriented perpendicular to the surface of substrate 10, resulting in a small surface area of ​​contact. In this configuration, the polishing action is concentrated at an annular region 40 on the top surface of substrate 10 with a small radial width. A central region 44 radially inward of annular region 40 is not polished.

[0052] While this specification contains details of many specific embodiments, these should not be construed as limitations on the scope of any invention or on the scope of what may be claimed, but rather as descriptions of features that may be unique to particular embodiments of a particular invention. Certain features that are described in this specification in the context of another embodiment can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented separately in multiple embodiments or in any suitable subcombination. Moreover, although features may be described above as working in certain combinations, or even initially claimed as such, one or more features from a claimed combination may in some cases be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0053] Similarly, while operations are depicted in the figures and recited in the claims in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown or sequential order, or that all of the illustrated operations be performed, to achieve desirable results. In certain environments, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together in a single software product or packaged into multiple software products.

[0054] Specific embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims may be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. The present application also includes the following aspects. (Aspect 1) a support configured to receive and hold a substrate in a plane; a polishing pad attached to the cylindrical surface of the rotary drum; a first actuator for rotating the drum about a first axis parallel to the plane; a second actuator that brings the polishing pad on the rotary drum into contact with the substrate at a position and orientation such that polishing is concentrated at an annular region on the top surface of the substrate and a central region radially inward of the annular region is not polished; a port for dispensing a polishing fluid at an interface between the polishing pad and the substrate; A polishing apparatus comprising: (Aspect 2) 2. The apparatus of embodiment 1, wherein the support is rotatable about a second axis. (Aspect 3) 3. The apparatus of claim 2, wherein the first axis is substantially perpendicular to a line extending from the second axis to a center point of the rotary drum. (Aspect 4) 2. The apparatus of embodiment 1, wherein the drum has a length greater than its diameter. (Aspect 5) 2. The apparatus of embodiment 1, wherein the drum has a length that is less than its diameter. (Aspect 6) 2. The apparatus of claim 1, further comprising: an in-situ monitoring system for monitoring the thickness of the substrate in an annular region adjacent to an edge of the substrate; and a controller configured to compare a first edge thickness profile to a second edge thickness profile to determine an edge thickness differential, and to cause the second actuator to move the polishing pad out of contact with the substrate when the edge thickness differential is less than a threshold value. (Aspect 7) 1. A method of chemical mechanical polishing a substrate, comprising: contacting a cylindrical polishing surface of a roller with the front surface of the substrate with the major axis of the roller parallel to the polishing surface; providing a polishing liquid to an interface between the polishing pad and the substrate; causing relative motion between the roller and the substrate to polish under-polished areas of the substrate without removing material from at least a portion of the front surface of the substrate, the relative motion including at least rotating the roller about the major axis while pressing the roller against the front surface of the substrate in a position and orientation such that polishing is concentrated at an annular region of the front surface of the substrate and a central region radially inward of the annular region is not polished; A method comprising: (Aspect 8) 8. The method of embodiment 7, wherein the cylindrical polishing surface extends across the edge of the substrate. (Aspect 9) 8. The method of embodiment 7, wherein an end of the cylindrical polishing surface is spaced radially inward of an edge of the substrate. (Aspect 10) 10. The method of embodiment 9, wherein opposing ends of the cylindrical polishing surface are located within 40 mm of the edge of the substrate. (Aspect 11) 8. The method of embodiment 7, comprising rotating the substrate about a second axis. (Aspect 12) 11. The method of embodiment 10, wherein the major axis is substantially perpendicular to a line segment extending from the second axis to a center point of the cylindrical polishing surface. (Aspect 13) 11. The method of embodiment 10, comprising rotating the substrate about the second axis at a speed of 1 to 500 rpm. (Aspect 14) 8. The method of claim 7, comprising rotating the cylindrical abrasive surface about the spindle at a speed of from 50 to 1500 rpm. (Aspect 15) 8. The method of embodiment 7, comprising pressing the cylindrical polishing surface into contact with the substrate at a pressure of 30 psi to 70 psi. (Aspect 16) 1. A method of chemical mechanical polishing a substrate, comprising: obtaining a thickness profile of the substrate; determining an angular asymmetry in polishing of the substrate from the thickness profile; and contacting a cylindrical polishing surface of a roller with a front surface of a substrate with a major axis of the roller parallel to the polishing surface; supplying a polishing liquid to a surface of the substrate; rotating the roller about the spindle while pressing the roller against the front surface of the substrate; at least one of decreasing the rotational speed of the substrate, increasing the rotational speed of the roller, or increasing the pressure of the roller against the front surface of the substrate as the under-polished region of the substrate passes under the roller to compensate for the angular asymmetry. A method comprising: (Aspect 17) 17. The method of embodiment 16, comprising obtaining the thickness profile from an in-line metrology system in a chemical mechanical polishing system. (Aspect 18) 18. The method of embodiment 17, wherein the in-line metrology system comprises a color imager, a spectroscopic sensor, an ellipsometer, or an eddy current sensor. (Aspect 19) 1. A method of chemical mechanical polishing a substrate, comprising: contacting a cylindrical polishing surface of a roller with a front surface of a substrate with a major axis of the roller parallel to the polishing surface; supplying a polishing liquid to a surface of the substrate; rotating the roller about the main axis while pressing the roller against the front surface of the substrate, the cylindrical polishing surface being positioned and oriented such that polishing is concentrated at an annular region of the front surface of the substrate and a central region radially inward of the annular region is spared; A method comprising:

Claims

1. a platen configured to receive and hold a substrate in a plane; a polishing pad attached to a cylindrical surface of a rotary drum having a length greater than its diameter; a first actuator for rotating the rotary drum about a first axis that is a main axis of the rotary drum and is parallel to the plane; a second actuator for contacting the polishing pad on the rotary drum only in an annular region adjacent the edge of the substrate; a port for dispensing a polishing fluid to an interface between the polishing pad and the substrate; an in-situ monitoring system for monitoring the thickness of the substrate within the annular region and generating two or more thickness profiles of the annular region, the two or more thickness profiles including a first thickness profile and a second thickness profile, the first thickness profile and the second thickness profile being pre- and post-polishing thickness profiles; a controller, comparing the first thickness profile to the second thickness profile to determine a thickness differential; rotating the platen such that the substrate rotates about a second axis that is perpendicular to the plane and passes through a center point of the substrate; adjusting the position of the center point of the rotary drum on the first axis in the length direction only along a line segment that is parallel to the plane and extends from the second axis to the center point of the rotary drum, thereby bringing the polishing pad into contact with the annular region on the front surface of the substrate, wherein the first axis of the rotary drum is parallel to the polishing pad, and both ends of the cylindrical polishing pad in the length direction are positioned radially inward from the edge of the substrate; supplying the polishing liquid to the port; causing relative motion between the polishing pad and the substrate by the first actuator to polish an under-polished area of ​​the annular region of the substrate without removing material from at least a portion of the front surface of the substrate outside the annular region, the relative motion including at least rotating the rotary drum about the first axis while pressing the rotary drum against the annular region of the front surface of the substrate; releasing the polishing pad from contact with the annular region by the second actuator when the thickness differential falls below a threshold value; a controller configured to A polishing apparatus comprising:

2. The apparatus of claim 1 , wherein the platen is rotatable about the second axis.

3. 1. A method of chemical mechanical polishing a substrate, comprising: rotating the substrate about an axis perpendicular to the plane of the substrate and passing through a center point of the substrate; adjusting the position of a center point of a roller on its major axis, the center point being parallel to the plane and extending from the axis to the center point of the roller, so that the cylindrical polishing surface of the roller contacts an annular area on the front surface of the substrate, the major axis of the roller being parallel to the cylindrical polishing surface and both ends of the cylindrical polishing surface in the length direction being spaced radially inward from the edge of the substrate; supplying a polishing liquid to an interface between the substrate and a polishing pad affixed to the cylindrical polishing surface of the roller; causing relative motion between the cylindrical polishing surface and the substrate to polish an under-polished area of ​​the annular region of the substrate without removing material from at least a portion of the front surface of the substrate outside of the annular region, the relative motion including at least rotating the roller about the major axis while pressing the roller against the annular region of the front surface of the substrate; A method comprising:

4. 4. The method of claim 3, wherein the cylindrical polishing surface extends across the edge of the substrate instead of having both ends of the cylindrical polishing surface in the length direction spaced radially inward from the edge of the substrate.

5. 4. The method of claim 3, wherein the ends of the cylindrical polishing surface along the length are located between 1 mm and 30 mm from the edge of the substrate.

6. 4. The method of claim 3, comprising rotating said cylindrical abrasive surface about said spindle at a speed of from 50 to 1500 rpm.

7. 4. The method of claim 3, comprising forcing the cylindrical polishing surface into contact with the substrate at a pressure of 30 psi to 70 psi.

Images