Patent ID: 12194591

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

DETAILED DESCRIPTION

Over the course of a CMP operation, the substrate thickness over the surface of the substrate can vary due to inconsistent polishing pad or carrier head pressure or dwell times or other inherent polishing non-uniformities. For example, some substrates are subject to a “check mark” non-uniformity in which an annular region near but not at the edge of the substrate is under-polished. In addition, the substrate edge can be subject to asymmetry.

CMP customers impose stringent film thickness uniformity thresholds on deliverable substrates. Typical CMP processes often achieve these thresholds for the majority of the central surface area of a substrate. However, interactions between substrate edge, polishing pad, and head retaining ring lead to non-uniformities in the edge region, including the “check mark” features, which cannot be eliminated by pressure control of the head zones. Moreover, incoming substrates can include non-uniform film thickness profiles that are challenging or impossible to correct with existing head technology, such as a pre-existing large edge thickness profile.

Various “touch-up” polishing processes have been proposed, e.g., using a small rotating disk-shaped polishing pad. However, such “touch-up” polishing processes contact the substrate in a small region and thus have low throughput.

Described herein is a location-specific polishing method. The method can provide substrate edge thickness profile correction. Material removal is accomplished by a polishing roller, e.g., a polishing pad affixed to the outer surface of a cylindrical roller. The parameters of the polishing roller, e.g., roller diameter, pad grit, can be selected to correspond to the substrate shape and/or thickness profile achieving flexibility in the design. Additionally, the polishing roller can be purchased conventionally or 3D printed, thereby realizing cost savings and reducing device down-time for maintenance. The controller functions to optimize substrate rotational speeds, polishing roller rotational speeds, and roller scanning profile to accomplish precise, location-specific material removal.

FIG.1illustrates an example chemical mechanical polishing apparatus100for polishing an under-polished region of a substrate. The polishing apparatus100includes a rotatable disk-shaped platen110on which a substrate10is situated. The platen110is operable to rotate about an axis114, for example, a motor can turn a drive shaft to rotate the platen110. The substrate10is held to the top surface of the platen110, e.g., by a vacuum applied to the bottoms surface of the substrate10by a vacuum source112, e.g., a vacuum chuck. The vacuum platen110maintains the substrate10orientation and position on the platen110while rotating about the axis114. The vacuum platen110provides the entire top surface of the substrate10to the polishing apparatus100and does not impede the polishing process.

The polishing apparatus100includes a first actuator operable to rotate a rotary drum118about a primary axis. A polishing pad119is affixed to at least a portion of the cylindrical outer surface of drum118, thus forming a cylindrical polishing surface. The drum118and affixed polishing pad119constitute a roller120. The roller120polishing surface is composed of a material suitable for polishing and planarization of the substrate10. The polishing pad material can be a polymer layer, e.g., polyurethane, and can be microporous layer, for example, an IC1000™ polishing layer material. The drum118ofFIG.1is cylindrical with a length longer than a diameter. The primary axis of rotation is coaxial with the longitudinal axis of the roller120. The roller120is arranged such that the primary axis is parallel with a front face, e.g., the upper surface, of the substrate10.

The polishing apparatus100includes a second actuator to control the vertical position of the roller120with respect to the substrate10and platen110. The second actuator operates to bring the roller120longitudinal surface into, and remove the roller120surface from, contact with the substrate10surface.

The polishing apparatus100includes a port130to dispense polishing liquid132, such as an abrasive slurry, onto the roller120. Alternatively, the port could dispense the polishing liquid directly onto the substrate10where it would be carried by rotation of the platen110below the roller120.

The polishing apparatus100can also include a polishing pad conditioner140, e.g., a diamond-embedded conditioner disk, to abrade the roller120surface to maintain the roller120in a consistent abrasive state. The pad conditioner140can be positioned adjacent the platen110in a face-up position generally coplanar with the top of the platen110or substrate10.

FIGS.2A and2Billustrate the operation of the polishing apparatus100utilizing one roller120and two rollers220, e.g., roller220aand roller220b, respectively. Referring toFIG.2A, the platen110supporting the substrate10rotates about axis114. The roller120is caused to rotate about the primary axis, such as by a second motor controlling the rotational motion of the roller120. The primary axis in the side-view ofFIG.2Aextends into the page.

The polishing liquid132is supplied to the roller120polishing surface via port130, as shown inFIG.1. In some embodiments, the polishing liquid132is supplied to the substrate10surface via port130. The roller120primary axis can be oriented at any angle in a range from 0° (e.g., parallel with) to 90° (e.g., perpendicular to) with respect to a ray (e.g., segment) connecting the substrate10centerpoint to the roller120centerpoint. For example, the roller120primary axis ofFIG.1is oriented perpendicular to (e.g., at 90° from) a ray connecting the substrate10centerpoint to the roller120centerpoint.

Referring toFIG.5A, as a region of the top surface near the substrate edge can often be underpolished, an implementation that can be of particular use is one in which the edges122of the roller120are positioned at or near, e.g., within 2 mm, of the edge12of the substrate10. In addition, the roller120is substantially perpendicular to (e.g., 80-90 from) the ray R connecting the substrate centerpoint14to the roller centerpoint124. In this configuration, the polishing action is concentrated at an annular region20of the top surface of the substrate10adjacent the substrate edge12, with higher polishing rate in a region22that is spaced apart from the substrate edge. A central region24radially inward of the annular region20is not polished. This configuration can be particularly well suited for compensating for the checkmark region. It should be noted that the polishing here occurs on the general planar surface of the substrate.

Alternatively, as shown inFIG.5B, the edges122of the roller120can be positioned radially inward, e.g., by 1-30 mm, from the edge12of the substrate10. Again, the roller120is substantially perpendicular to (e.g., 80-90° from) the ray R connecting the substrate centerpoint14to the roller centerpoint124. In this configuration, the polishing action is concentrated at an annular region30of the top surface of the substrate10that is spaced apart from the substrate edge12. There may be a higher polishing rate in a region32that is closer to the inner diameter of the annular region30. A central region34radially inward of the annular region30and a second annular region36surrounding the polished annular region30are not polished. This configuration can also be well suited for compensating for the checkmark region.

Returning toFIG.1, the roller120is brought into contact with the front face of the substrate10creating a contact area between the roller120polishing surface and the substrate10front face. The polishing apparatus100commands the second actuator to apply a force to the roller120, e.g., pressed, in a direction orthogonal to and toward the substrate10, e.g., down inFIG.2A. The force applied to the contact area via roller120can be in a range from 30 psi to 70 psi (e.g., 40 psi to 50 psi, or 60 psi to 70 psi).

The rotational motion of the roller120polishing surface in the presence of the polishing liquid132causes a portion of the substrate10material in the contact area to be removed, e.g., polished, while not removing substrate10material outside of the contact area. If necessary, the roller120can be moved along an axis parallel to the plane of the substrate10, e.g., right to left inFIG.2A, to reposition the contact area along the substrate10front face. The substrate10rotation and roller120rotational and translational motion create a relative motion between the roller120and the substrate10front face. While in contact with the substrate10the roller120rotational speed can be in a range from 10 rpm to 2500 rpm (e.g., 50 rpm to 1500 rpm).

The time period in which the roller120polishing surface is in contact with the substrate10is a contact time. The dwell time of the roller over any particular region, in conjunction with the pressure and rotation rates, determine the amount of material removed from the substrate. After the contact time between the roller120and the substrate10, the roller120polishing surface, the roller120can be removed from the substrate10to stop polishing. The contact time can be in a range from less than 1 s to 600 s.

After a polishing operation is complete, the polishing surface can be reconditioned by removing the roller120from the substrate10front face and contacting the roller120polishing surface to the pad conditioner140. For example, the second actuator can move the roller horizontally from a position over the substrate to a position over the pad conditioner140. The polishing apparatus100causes roller120rotational motion while in contact with the pad conditioner140thereby abrading an outer layer of the roller120polishing surface. The roller120remains in contact with the pad conditioner140while continuing to rotate for a conditioning time. In some embodiments, additional relative motion between the roller120and pad conditioner140can include translating the roller120along an axis parallel with the pad conditioner140surface.

FIG.2Billustrates another implementation of a polishing apparatus200that includes roller220aand roller220b(collectively rollers220), to polish the substrate10. The substrate10rotates about axis114on the platen110. Two ports,230aand230b, (collectively ports230) are positioned adjacent rollers220aand220b, respectively, supplying polishing liquid132to each. In such embodiments, the rollers220can be substantially the same, or different, including length, diameter, compressibility, elasticity, and material composition of the polishing surface. For example, the polishing surface of roller220amay have a first durometer value, and the polishing surface of roller220bmay have a different second durometer value.

Rollers220aand220b(collectively rollers220) can create substantially the same, or different, relative motion between the substrate10and the respective rollers220aand220b, including respective rotational- and/or translational speeds, translational axis-, and/or primary axis-orientation.

The polishing apparatus200includes two pad conditioners240, pad conditioner240aand240brespectively. The pad conditioners240can be substantially the same material, or different, and include substantially the same abrasive capability (e.g., grit), or different. For example, the conditioning surface of roller pad conditioner240amay have a first durometer value, and conditioning surface of roller pad conditioner240bmay have a different second durometer value. The rollers220can be operated to contact the pad conditioners240concurrently or differentially.

Embodiments including two or more rollers220can reduce substrate10polishing time, thereby decreasing material and time costs associated with substrate10polishing.

The contact time, roller120rotational- and translational speed, and pressure parameters can be determined based upon the amount of material removed to achieve thickness profile limits and compose a correction profile. The correction profile can be loaded into a controller of the polishing apparatus100to control the platen110, roller120, and132flow rate.FIG.3is a chart comparing the material removed from the surface of the substrate10on the y-axis to wafer radial location on the x-axis. The y-axis depicts a range of material removed from 0 Angstroms (Å) to 240 Å. A higher y-axis value indicates that more material was removed from the substrate10surface at the corresponding x-axis radial location. The x-axis includes radial locations in a range from 120 mm to 150 mm.FIG.3includes lines depicting two surface profiles, the first surface profile320aand second surface profile320b, which extend from 120 mm to 145 mm on the x-axis.

Surface profile320ais a calculated average profile of eight measured surface profiles as measured along eight lines extending radially from the center of the substrate10from 120 mm to 145 mm, wherein the eight lines are oriented with even radial spacing around the circumference of the substrate10.

The polishing apparatus100was operated to polish the substrate10according to two correction profiles. The first correction profile corresponding to surface profile320aincluded a pressure parameter of 45 psi, and the roller120was positioned at five radial locations for five respective time periods totaling 125 seconds of dwell time. The initial roller120location was approximately 137 mm, the second location approximately 135 mm, the third location approximately 133 mm, the fourth location approximately 131 mm, and the fifth location approximately 128 mm along a radial ray from the substrate10center.

The roller120had dwell times of 35 s, a 30, 25 s, 20 s, and 15 s at the first, second, third, fourth, and fifth radial locations, respectively. Thereafter the roller120was removed from contact with the substrate10. This creates a sloped surface profile320ain which the roller120removed a larger amount of material at the outermost radial location (137 mm) and removed consecutively less material at successively inwardly positioned radial locations.

The second correction profile corresponding to surface profile320bincluded a pressure parameter of 45 psi, and the roller120was positioned at four radial locations a radial line for four 15 s time periods totaling 60 s of dwell time. The initial roller120location was approximately 131 mm, the second location approximately 133 mm, the third location approximately 136 mm, and the fourth location approximately 139 mm along a radial ray from the substrate10center.

The roller120had dwell times of 15 s at each radial location, respectively, and thereafter the roller120removed from contact with the substrate10. This creates a sloped surface profile320bwherein the roller120removed a smaller amount of material at the outermost radial location (137 mm) and removed consecutively more material at successively inwardly positioned radial locations.

FIG.4is a is a chart comparing substrate10surface height in Angstroms as measured along a line extending as a ray from the substrate10centerpoint on the y-axis to radial location in mm on the x-axis.FIG.4includes two edge profiles,420aand420b. Edge profile420acorresponds with a substrate10surface before the polishing apparatus100polishes the surface using a correction profile. Edge profile420ais approximately planar at 14,500 Å between 125 mm and 135 mm on the x-axis. Between 135 mm and 150 mm, the measured substrate10surface corresponds to an increasing surface height to an approximate 15,300 Å height before reducing to a value of approximately 14,900 Å at 149 mm on the x-axis.

Edge profile420bdepicts the substrate10surface after the polishing apparatus100polished the substrate10according to a correction profile in which the parameters were designed to correct the edge profile420ato an approximately planar substrate10surface. The polishing apparatus100achieved an approximately planar substrate10surface along the measured surface, as shown in edge profile420b.

In some embodiments, the polishing apparatus100includes an in-situ monitoring system to monitor one or more thicknesses of the substrate. Examples of in-situ monitoring systems include optical monitoring, e.g., spectrographic monitoring, eddy current monitoring, acoustic monitoring, and motor torque monitoring. The in-situ monitoring system determines a thickness, such as a thickness relative to the edge12or relative to central region24, at one or more radial positions within an annular region, such as annular region20or annular region30. The polishing apparatus100controller constructs a thickness profile from the one or more thicknesses. In some embodiments, a thickness profile can be determined using an in-line metrology system. Examples of in-line monitoring systems include optical monitoring, e.g., a color imager, spectrographic sensor, or ellipsometer, or an eddy current sensor.

For example, a first thickness profile can be determined from an annular region20on the substrate10surface. An annular region20in which the outer radius is aligned with the substrate edge12produces an edge-thickness profile. The polishing apparatus100contacts the annular region20with roller120and polishes the annular region20for a time interval.

The polishing apparatus100determines a second thickness profile using the in-situ monitoring system of the annular region20(e.g., a second edge-thickness profile). The polishing apparatus100compares 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 the edge-thickness difference determined during the polishing. When the edge-thickness difference is below a threshold stored in the polishing apparatus100, the polishing apparatus100causes the second actuator to bring the polishing pad out of contact with the chart comparing substrate10.

The roller120can be constructed to conform to different shape profiles. The examples described above include a horizontally-oriented cylindrical roller120though in some embodiments, the roller120can be wheel-shaped, in which the radius is larger than the length of the roller120. Such embodiments provide a lower roller620contact surface with the substrate60and increase the polishing spatial resolution.

FIG.6Ashows an example polishing apparatus600including a wheel-shaped roller620coupled to a motor650. The roller620is in contact with the substrate60arranged on a platen610including a vacuum source612to maintain the position and orientation of the substrate60on the platen610during polishing. The polishing apparatus600dispenses polishing liquid632onto the substrate60surface via port630and operates the motor650causing rotational motion in the roller620when in contact with the substrate60. The polishing apparatus600includes pad conditioner640to abrade and re-condition the roller620. As inFIG.2B, the polishing apparatus600can include more than one roller620, and/or more than one pad conditioner640for each respective roller620.

The platen610rotates around a first vertical central axis and the roller620rotates about a second axis perpendicular to the first, and parallel with the substrate60surface. In some embodiments, the motor650can translate the roller620along the second axis to cause relative motion between the substrate60and roller620in a third dimension, which can be in addition or alternative to the motion along the first and second rotational axes.

FIG.6Bdepicts a side view along the roller620second rotational axis, e.g., in-line with the motor650rotational axis. The roller620includes a rigid central drum622around which an inflatable support tube624encompasses. The support tube624provides at least a portion of the pressure applied to the pad626when in contact with the substrate60. In some embodiments, the support tube624is inflated to a pressure in a range from 1 psi to 50 psi. In various example embodiments, the support tube624inflation pressure is a parameter controlled by the polishing apparatus600in a correction profile to achieve an edge profile, such as planar edge profile420b.

Referring toFIG.6C, a top view of the implementation ofFIGS.6A and6Bis shown. Such implementations can be of particular use for increasing the polishing spatial resolution by decreasing the contact area of the roller620. The roller620is substantially perpendicular to (e.g., 80 to 90° from) the ray R connecting the substrate centerpoint14to the roller centerpoint625.

While the rollers120ofFIGS.5A and5Bwere cylindrical and oriented such that the length was parallel with the substrate10surface, achieving a high surface area contact area, roller620is a wheel oriented perpendicular to the substrate10surface resulting in a low surface area contact area. In this configuration, the polishing action is concentrated at an annular region40of the top surface of the substrate10with a low radial width. A central region44radially inward of the annular region40is not polished.

While this specification contains many specific implementation details, 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 specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments 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 in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially be claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

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

Particular 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 can 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.