Monitoring thickness of face-up polishing

Abstract

A chemical mechanical polishing system includes: a support configured to hold a substrate facing upward; a polishing article having a smaller polishing surface than the exposed surface of the substrate; a port for dispensing the polishing liquid; one or more actuators for contacting the polishing surface with a first portion of the exposed surface of the substrate and producing relative movement between the substrate and the polishing pad and the optically transmissive polymer window; an in-situ optical monitoring system; and a controller configured to receive the signal from the optical in-situ monitoring system and modify the polishing parameter based on the signal. The optical monitoring system includes a light source and a detector, and the in-situ optical monitoring system is configured to direct a light beam from above the support to impinge on a non-overlapping second portion of the exposed surface of the substrate.

Description

Technical Field

[0001] The present disclosure relates to in-situ monitoring of chemical mechanical polishing, and in particular to layer thickness monitoring of face-up polishing. Background Art

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing a conductive layer, a semiconductive layer, or an insulating layer on a silicon wafer. One manufacturing step involves depositing a filler layer above a non-planar surface and flattening the filler layer. For some applications, the filler layer is flattened until the top surface of the patterned layer is exposed. For example, a conductive filler layer can be deposited on a patterned insulating layer to fill a groove or hole in the insulating layer. After flattening, the portion of the metal layer remaining between the raised patterns of the insulating layer forms a through hole, plug, and line that provides a conductive path between the thin film circuits on the substrate. For other applications, such as oxide polishing, for example, the filler layer is flattened by polishing for a predetermined period of time to leave a portion of the filler layer above the non-planar surface. In addition, flattening of the substrate surface is generally required for photolithography.

[0003] Chemical mechanical polishing (CMP) is an accepted planarization method. This planarization method generally requires mounting the substrate on a carrier or polishing head. The exposed surface of the substrate is generally placed against a rotating polishing pad in a "face down" orientation. The carrier head provides a controllable load through one or more pressure actuators to push the substrate against the polishing pad. An abrasive polishing slurry is generally supplied to the surface of the polishing pad.

[0004] To compensate for radial variations in thickness due to variations in access to the substrate or variations in polishing rate caused by the polishing apparatus, sensors may be scanned across the substrate during polishing and radially disposed chambers in the carrier head may be driven to different pressures. Summary of the invention

[0005] Disclosed herein is a system and method for monitoring the thickness value of an exposed layer of a substrate in "face-up" chemical mechanical polishing. The substrate is arranged on a vacuum support so that the surface of the substrate to be planarized is exposed to contact with a rotating polishing article. The polishing article is brought into contact with the exposed surface and rotated, thereby polishing a portion of the exposed surface.

[0006] The system includes an optical in-situ monitoring system configured to direct a light beam onto an exposed surface of a substrate and receive light reflected from the exposed surface of the substrate. The optical system receives the reflected light and generates a signal indicating a thickness of a material layer on the exposed surface. The optical monitoring system communicates with a controller of the system and sends a signal to the controller. The controller receives the signal and modifies a polishing parameter based on the signal.

[0007] In one aspect, a chemical mechanical polishing system includes: a support configured to receive and hold a substrate in a face-up orientation; a polishing article having a polishing surface that is smaller than an exposed surface of the substrate; a port for dispensing a polishing liquid to an interface between a polishing pad and the substrate; one or more actuators for contacting the polishing surface with a first portion of the exposed surface of the substrate and generating relative motion between the substrate and the polishing pad and an optically transmissive polymer window; an in-situ optical monitoring system; and a controller configured to receive a signal from the optical in-situ monitoring system and modify a polishing parameter based on the signal. The optical monitoring system includes a light source and a detector, and the in-situ optical monitoring system is configured to direct a light beam from above the support to impact a non-overlapping second portion of the exposed surface of the substrate.

[0008] In another aspect, the present disclosure features a chemical mechanical polishing system, the chemical mechanical polishing system comprising: a support configured to receive and hold a substrate; a polishing article having a polishing surface that is smaller than an exposed surface of the substrate; a port for dispensing a polishing liquid to an interface between a polishing pad and the substrate; an in-situ optical monitoring system; and one or more actuators, including a controller, configured to receive a signal from the optical in-situ monitoring system and modify a polishing parameter based on the signal. The in-situ optical monitoring system includes a light source, a detector, and an optically transmissive polymer window. The light source is configured to direct a light beam through the optically transmissive polymer window and the detector is configured to receive a reflection of the light beam through the optically transmissive polymer window. The one or more actuators are configured to contact the polishing surface with a first portion of the exposed surface of the substrate, contact the optically transmissive polymer window with a non-overlapping second portion of the exposed surface of the substrate, and generate relative motion between the substrate and the polishing pad and the optically transmissive polymer window.

[0009] In another aspect, a chemical mechanical polishing system includes: a support configured to receive and hold a substrate; a polishing article having a polishing surface that is smaller than an exposed surface of the substrate; a port for dispensing a polishing liquid to an interface between a polishing pad and the substrate; an in-situ optical monitoring system; and one or more actuators, including a controller, configured to receive a signal from the optical in-situ monitoring system and modify a polishing parameter based on the signal. The in-situ optical monitoring system includes a light source, a detector, and an optically transmissive polymer window. The light source is configured to direct a light beam directly onto the substrate, through the optically transmissive polymer window, through a column of water in contact with the substrate, and the detector is configured to receive a reflection of the light beam directly from the substrate, through the optically transmissive polymer window, or through a column of water in contact with the substrate. The one or more actuators are configured to contact the polishing surface with a first portion of the exposed surface of the substrate, to bring the in-situ optical monitoring system over a non-overlapping second portion of the exposed surface of the substrate, and to generate relative motion between the substrate and the polishing pad and the in-situ optical monitoring system.

[0010] Features may include one or more of the following.

[0011] The optical in-situ monitoring system may include one or more optical fibers for carrying light from a light source to a window and carrying reflected light reflected from a substrate and carrying the reflected light to a detector through the window. The first axis may be substantially perpendicular to a section extending from the second axis to a center point of the roller. The relative motion may include moving the polishing surface parallel to a plane of the polishing surface. The optical in-situ monitoring system may be configured to direct a light beam onto an edge portion of a substrate, wherein a cylindrical polishing surface extends across the surface of the substrate. The ends of the cylindrical polishing surface may be radially spaced inward from the edge of the substrate. The opposite ends of the cylindrical polishing surface are positioned within 40 mm of the edge of the substrate. The angular orientation of the substrate may be determined based on the received reflected signal. The controller may be configured to determine the thickness of the topmost layer of the substrate, or the thickness profile of the topmost layer of the substrate.

[0012] Particular embodiments of the objectives described in this specification may be implemented to achieve one or more of the following technical advantages. Wafer-to-wafer (WTW) and within-wafer (WIW) polishing uniformity may be improved. Radial and angular non-uniformities may be reduced. Determining polishing parameters for a polishing operation facilitates directing the polishing operation to achieve a desired polishing profile. This polishing profile may be fed into an algorithm to increase material removal accuracy.

[0013] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic cross-sectional view of an example of a polishing apparatus is shown.

[0015] Figure 2 A perspective view of a polishing system with an in-situ optical monitoring system is shown.

[0016] Figure 3A and Figure 3B 1 and 2 are diagrams respectively showing the polishing area and the path of the transmission window.

[0017] Figure 4 is a flow chart detailing the polishing method.

[0018] Figure 5 A schematic cross-sectional view illustrating another embodiment of an in-situ optical monitoring system is shown.

[0019] Figure 6 A schematic cross-sectional view showing yet another embodiment of an in-situ optical monitoring system is shown.

[0020] Fig. 7AA schematic top view of a circular polishing pad on a substrate is shown.

[0021] Figure 7B Shows Fig. 7A Schematic cross-sectional view of a polishing system.

[0022] Fig. 8A A schematic top view of a curved polishing pad on a substrate is shown.

[0023] Figure 8B Shows Fig. 8A Schematic cross-sectional view of a polishing system.

[0024] In the drawings, like reference numerals refer to like elements. DETAILED DESCRIPTION

[0025] In addition to radial variations in thickness, in some semiconductor chip manufacturing processes, there are angular variations in thickness (e.g., depending on the azimuth around the center of the substrate). Like radial variations, angular variations can be attributed to variations in access to the substrate or to variations in polishing rate caused by the polishing device. Various "touch-up" polishing processes have been proposed, for example, using a small rotating dish-shaped polishing pad. However, such "touch-up" polishing processes contact the substrate in a small area and therefore have a low throughput. "Touch-up" polishing may also be referred to as location-specific polishing (LSP).

[0026] A location-specific polishing method is described herein that uses data collected in real time from an exposed surface of a substrate as measured by an in-situ optical monitoring system. A system controller receives data indicating layer thickness at the exposed surface and modifies one or more polishing parameters to achieve a target thickness profile.

[0027] The parameters of the polishing roller (e.g., roller diameter, pad particle size, etc.) can be selected based on the substrate shape and / or thickness profile, thereby providing flexibility for different polishing processes. In addition, the polishing roller can be purchased conventionally or 3D printed, thereby achieving cost savings and reducing equipment downtime for maintenance. The controller is used to optimize the substrate rotation speed, polishing roller rotation speed and pressure, roller orientation, and roller scanning profile to achieve precise, location-specific material removal.

[0028] See also Figure 1 and Figure 2 , Figure 1 An example of a polishing system 100 is shown, and Figure 2A perspective view of an exemplary polishing system 100 is shown. The polishing system 100 includes a rotatable dish-shaped chuck 120 on which the substrate 10 is located. As an installed system, the chuck 120 holds the substrate in a "face-up" orientation, i.e., the flat top surface 12 to be polished is substantially perpendicular to gravity and oriented so that the top surface 12 will support polishing liquid dispensed onto the top surface 12 (although the polishing liquid can be thrown off by rotation of the substrate 10).

[0029] The chuck 120 is operable to rotate about a rotation axis 125. For example, an actuator (e.g., a motor 121, such as a DC induction motor) can turn a drive shaft 124 to rotate the chuck 120. In operation, the substrate 10 is held to the top surface of the chuck 120, for example, by a vacuum applied to the bottom surface 14 of the substrate 10 by a vacuum source 112 (e.g., a vacuum chuck). The vacuum chuck 120 maintains the orientation and position of the substrate 10 on the chuck 120 while rotating about the rotation axis 125. The vacuum chuck 120 exposes the entire surface (e.g., the top surface) of the substrate 10 to the polishing system 100 and does not hinder the polishing process.

[0030] The polishing system 100 includes a rotating drum 118 operable to rotate about a primary rotation axis 162 (see Figure 2 ; axis extends out Figure 1 The polishing layer 119 is fixed to at least a portion of the cylindrical outer surface of the drum 118, thereby forming a cylindrical polishing surface 119a. The drum 118 and the fixed polishing layer 119 constitute a polishing roller 160. Figure 1 The roller 118 is cylindrical with a length greater than a diameter. The main rotation axis 162 is coaxial with the longitudinal axis of the roller 160. The roller 160 is arranged so that the main axis is parallel to the front side (e.g., the exposed upper surface) of the substrate 10. In addition, the rotation axis 162 can be perpendicular to a radial section extending from the rotation axis 125 of the chuck to the longitudinal midpoint of the portion of the roller 160 that contacts the polishing surface 119a.

[0031] The polishing surface 119a of the roller 160 is composed of a material suitable for polishing and planarizing the substrate 10. The polishing layer 119 may include one or more layers. The outermost layer of the polishing layer 119 is a polishing layer. The material of the polishing layer may be a polymer, such as polyurethane, and may be a microporous layer, such as an IC1000 polishing layer material.

[0032] The polishing system 100 may include a port 130 for dispensing a polishing liquid 132, such as an abrasive slurry, onto the polishing substrate 10, where the polishing liquid will be carried under the roller 160 by the rotation of the chuck 120 and the substrate 10. Alternatively, the port may dispense the polishing liquid directly onto the roller 160.

[0033] The polishing system 100 includes a second actuator for controlling the vertical position of the roller 160 relative to the substrate 10 and the chuck 120. The second actuator operates to bring the polishing surface of the roller 160 into contact with the surface of the substrate 10 and remove the polishing surface of the roller 160 from contact with the surface of the substrate 10. In the polishing operation, the roller 160 is brought into contact with the front face of the substrate 10, thereby establishing a contact area between the polishing surface of the roller 160 and the front face of the substrate 10. The polishing system 100 commands the second actuator to apply a force, e.g., a press, to the roller 160 in a direction orthogonal to the exposed surface (e.g., toward the substrate 10). The force applied to the contact area via the roller 160 may be in the range of from 0.5 to 5 psi.

[0034] The rotational movement of the polishing surface of roller 160 in the presence of polishing liquid 132 results in the removal (e.g., polishing) of a portion of the material of substrate 10 in the contact area without removing material of substrate 10 outside the contact area. If necessary, roller 160 can be moved along an axis parallel to the plane of substrate 10, for example, in Figure 1 10, for repositioning the contact area along the front side of the substrate 10. The rotation of the substrate 10 and the rotational and translational motion of the roller 160 create relative motion between the roller 160 and the front side of the substrate 10. The rotational speed of the roller 160 when in contact with the substrate 10 may be in the range of from 10 rpm to 2500 rpm (e.g., 50 rpm to 1500 rpm).

[0035] The period of time that the roller 160 is in contact with the substrate 10 is the contact time. The residence time of the roller over any particular area in combination with the pressure and rotation rate determines the amount of material removed from the substrate. After the contact time between the roller 160 and the substrate 10, the roller 160 can be removed from contact with the substrate 10 to stop polishing.

[0036] The azimuthal polishing profile can be controlled by synchronizing roller pressure or position with chuck rotation (at low chuck speeds), for example, to correct for asymmetry.

[0037] A controller 190 (such as a programmable computer) is connected to the motor 121 to control the rotation rate of the chuck 120. For example, the motor 121 may include an encoder that measures the rotation rate of the associated drive shaft. A feedback control circuit (which may itself be in the motor 121, part of the controller 190, or a separate circuit) receives the measured rotation rate from the encoder and adjusts the current supplied to the motor 121 to ensure that the rotation rate of the drive shaft matches the rotation rate received from the controller 190.

[0038] The system 100 includes a position sensor 140 to sense the angular position of the chuck 120 or the substrate 10. This allows for orientation of the substrate 10 relative to the chuck 120, relative to a polishing profile stored in the controller 190, or both.

[0039] For example, the position sensor may be an optical sensor positioned near the rim of the chuck 120 and such that the sensor will cover the annular edge of the substrate. The substrate 10 may include a notch 142 (see Figure 2 ) or plane (see Figure 3A and Figure 3B ). Thus, due to the rotation of the substrate 10 and the chuck 120, the position sensor 140 intermittently passes through the notch 142 or plane, causing a change in reflectivity, which is optically detected by the sensor 140. As another example, the optical sensor 140 can be an optical interrupter. Specifically, the sensor 140 can include a light source and a detector, and a tab can extend from the edge of the chuck. Due to the rotation of the chuck, the tab will intermittently pass between the light source and the detector, interrupting the light beam, which is optically detected by the sensor. The frequency of the detection of the notch or optical interruption provides the rotation rate of the chuck and substrate 10.

[0040] The polishing system 100 includes an in-situ optical monitoring system 180 for measuring a signal indicative of the thickness of an exposed layer of the surface of the substrate 10. The optical monitoring system 180 includes a light source 182 and a sensor 184 coupled to an optically transmissive window 150. In operation, the window 150 is brought into physical contact with the top surface 12 of the substrate 10.

[0041] Light source 182 generates light that is transmitted to window 150 through a connection (such as, through optical fiber 186, for example, a fiber optic cable). In some embodiments, light source 182 is a laser, a flash lamp, or a discharge lamp. In one example, the light is a wide spectrum across visible wavelengths, for example, white light. In an alternative example, the light has a bandwidth that includes a portion of the visible wavelengths, such as a 10nm bandwidth, or a 100nm bandwidth. Light source 182 can include any necessary filters, reflectors, or diffraction gratings to generate light of a selected spectrum or bandwidth.

[0042] The window 150 is composed of a transmissive material, for example, having a transmittance of at least 90%, at least 95%, or at least 99% for the wavelength monitored by the detector, which is chemically compatible with the polishing process. The window 150 has sufficient durability to withstand the friction generated by the contact between the window 150, the substrate 10, and the polishing liquid 132. The window 150 can be a solid, for example, a substantially non-porous polymer body. Suitable polymers include polyurethane, polycarbonate, polymethyl methacrylate (PMMA), acrylic, polyethylene terephthalate glycol (PET), or amorphous copolyester (PETG). In some embodiments, the window 150 is formed of the same polymer composition as the polishing layer of the polishing layer 119 on the roller 118. In some embodiments, the polishing layer of the polishing layer 119 is a polymer matrix having pores, for example, liquid-filled pores or hollow microspheres, and the window 150 is formed of the same polymer matrix but without pores. In some embodiments, the matrix materials of the window 150 and the polishing layer 119 use the same two (or more) monomeric or polymeric components, but with different weight percentage contributions in order to provide different compressibility.

[0043] Window 150 contacts the top surface of substrate 10. Light forms a light beam 152 that is transmitted through window 150, reflected from the top surface of substrate 10, and reflected back through window 150. The reflected light is received, for example, by optical fiber 186, and transmitted to optical sensor 184 of optical monitoring system 180. For this configuration, light beam 152 strikes substrate 10 orthogonally to exposed surface 12. Optical sensor 184 may be a spectrometer.

[0044] Sensor 184 receives light reflected from window 150, and optical monitoring system 180 determines a thickness profile indicative of the thickness of the layer of the substrate beneath window 150 based on the signal from sensor 184. Controller 190 may store a target thickness profile of the layer of substrate 10 being polished.

[0045] See again Figure 1 and Figure 2During the polishing operation, the contact time, the rotational and translational speed of the roller 160, and the pressure parameters can be determined based on the amount of material removed to achieve the target thickness profile and constitute the correction profile. The correction profile can be loaded into the controller of the polishing system 100 to control the flow rate of the chuck 110, the roller 160, and the liquid 132. For example, the controller 190 controls the polishing parameters of the polishing operation to achieve the target thickness profile. Some examples of polishing parameters include the rotational speed (e.g., of the chuck 120 or the roller 160), the pressure (e.g., of the roller 160), the contact time, the translational speed, the orientation angle, or the polishing area (e.g., the annular area 30). Specific examples of polishing parameters include one or more of the following: the pressure of the polishing pad against the substrate, the lateral position of the polishing surface relative to the substrate, the movement rate of the polishing surface relative to the substrate, the polishing endpoint, the rotational rate of the roller, or the angle of the spindle relative to the radius of the substrate.

[0046] See also Figure 3A , the major axis of the roller 160 can be oriented at any angle ranging from 0° (e.g., parallel) to 90° (e.g., perpendicular) relative to a ray (e.g., segment) connecting the center point 15 of the substrate 10 to the center point 126 of the roller 160. For example, Figure 4 The major axis of roller 160 of A is oriented perpendicular to (eg, at 90° thereto) a ray connecting center point 15 of substrate 10 to center point 134 of roller 160 .

[0047] The edge of the roller 160 is positioned at or near the edge 13 of the substrate 10, or radially inward (e.g., up to 1-30 mm) from the edge 13. In some embodiments, the roller 160 is substantially perpendicular to (e.g., 80-90° thereto) a ray connecting the substrate center point 15 to the roller center point 126. The roller 160 contacts the substrate 10 over a portion of the surface, and in this configuration, the polishing action is concentrated at an annular region 30 of the top surface of the substrate 10 spaced from the substrate edge 13. In other words, the portion of the substrate that contacts the roller 160 and rotates about the center point 15 forms the annular region 30. The central region 34 radially inward from the annular region 30 and the second annular region 36 surrounding the polished annular region 30 are not polished.

[0048] Figure 3B A top view of substrate 10 during a polishing operation is shown, wherein window 150 is formed by passing adjacent Figure 3B15. The window 150 moves in a direction as indicated by the double-sided arrow of the window 150 in FIG. 15. In some embodiments, the direction is in a radial direction, such as between a point on the edge 13 and the center point 15. As the substrate 10 rotates with the chuck 120 in the direction of motion 16, the window 150 follows a spiral path 38 toward the center point 15. The size of the window 150 determines the portion of the substrate 10 that the window 150 covers while following the path 38. The portion that the window 150 contacts, and the portion that the roller 160 contacts, are non-overlapping.

[0049] See now Figure 4 , a flow chart outlining a method 400 of polishing a substrate is illustrated. The method 400 includes.

[0050] The method includes contacting the face of substrate 10 with roller 160 (step 402). The polishing surface of roller 160 rotates about a primary axis of rotation parallel to the surface being polished.

[0051] The method includes supplying polishing liquid 132 to the interface between roller 160 and substrate 10 (step 404). Polishing liquid 132 may include abrasive particles suspended in a carrier fluid, such as an abrasive slurry. Port 130 of system 100 dispenses liquid 132 onto the polishing surface of substrate 10.

[0052] The method includes contacting the window 150 of the in-situ optical monitoring system 180 with the face of the substrate (step 406). In some embodiments, the detector 184 of the optical monitoring system 180 is optically coupled to the transparent optical window 150 through an optically transmissive connection, such as a fiber optic cable.

[0053] The method includes causing relative motion between the substrate 10 and the roller 160 (step 408). Relative motion can also be generated between the substrate 10 and the window 150. An example of relative motion includes rotating the polishing surface of the roller 160 about a main axis while pressing the polishing surface against the exposed front face of the substrate 10. Additionally or alternatively, rotating the chuck 120 supporting the substrate 10 causes relative motion between the substrate 10 and both the roller 160 and the window 150. The relative motion can be between the substrate 10 and the window 150, or it can be generated by sweeping the window laterally (e.g., radially) across the substrate 10. This lateral motion can be combined with the rotation of the chuck 120 to produce a spiral sweep of the window 150 across the substrate 10.

[0054] The method includes monitoring a signal from an in-situ optical monitoring system 180 (step 410). A light source 182 generates light that is transmitted to a window 150. The light is reflected from an exposed surface of the substrate 10 that contacts the window 150. The reflected light is captured by a detector 184, or alternatively captured by a fiber optic connection that connects the window 150 to the detector 184. The optical monitoring system 180 generates a thickness signal based on the reflected light. Alternatively, the optical monitoring system 180 transmits a measurement of the reflected light to a system controller 105 that generates a thickness signal. Because the window 150 is swept laterally across the substrate 10, the system can generate a thickness profile, for example, a radial thickness profile.

[0055] The method includes modifying polishing parameters based on the measured thickness profile that meets the desired polishing criteria (step 412). The system controller 105 receives the measured thickness profile and compares the measured thickness profile to the target profile. If the difference between the measured thickness profile and the target profile exceeds a threshold, the system controller 105 may change one or more polishing parameters, such as the position or rotational speed of the roller, to compensate. Alternatively or additionally, the system controller 105 may pause polishing once the measured thickness profile matches the target thickness profile.

[0056] Although the above description focuses on a window contacting a substrate, several other techniques may be used.

[0057] For example, a beam of light can be transmitted through a "water column" to the substrate surface. Figure 5 , a barrier 200 having a hole 202 therethrough can be placed in contact with the exposed surface 12 of the substrate 10. A transparent liquid 210 (e.g., water) is placed in the hole 202 to form a "water column" of transparent liquid in contact with the exposed surface 12 of the substrate 10. The barrier 200 can hold the transparent liquid 210 to provide the water column and prevent the slurry 132 from mixing with the transparent liquid 210 to reduce noise. The end 187 of the optical fiber 186 is placed in the transparent liquid 210 so that the light beam 152 passes through the "water column" of transparent liquid 210 to impact the substrate and reflect back from the substrate. In this case, Figure 4 As shown 406 will include contacting the water column with the face of the substrate.

[0058] As another example, the slurry can be blown away from the exposed surface of the substrate using a gas jet. Figure 6, the nozzle 220 is positioned above the substrate. A gas (e.g., pure air or nitrogen) is directed through the nozzle 220 to form a jet 222 of gas. The nozzle 220 is positioned so that the jet 222 of gas blows any polishing liquid 132 away from an area 224 of the substrate where the light beam 152 impacts the exposed surface of the substrate 10. This prevents the polishing liquid (e.g., abrasive particles in the polishing liquid) from scattering a portion of the light beam and generating noise in the measurement signal. In this case, the detector of the in-situ monitoring system is in contact with the face of the substrate. In this case, Figure 4 As shown 406 will be replaced by blowing the polishing liquid away from the face of the substrate.

[0059] Furthermore, although the above description focuses on rollers having cylindrical polishing layers, the optical monitoring techniques discussed above (e.g., for Figure 1 , Figure 5 and Figure 6 ) can be used with other polishing layer configurations.

[0060] For example, the polishing system may use a rotatable circular dish-shaped polishing pad that is smaller than the substrate. Fig. 7A and Figure 7B , a circular polishing layer 119' (i.e., polishing pad) can be held on the bottom of a pad carrier 250 (e.g., a metal disk). The pad 119' contacts only a portion of the substrate 10. In some embodiments, the pad carrier 250 is rotated by a drive shaft 252 driven by a motor 254. The motor 254 can rotate the polishing pad 119' about an axis 256 that passes through the center of the polishing pad 119'. In some embodiments, the axis 256 is slightly offset from the center of the polishing pad 119' so that the pad performs an orbital motion on the substrate. In either case, due to the rotation of the chuck 120, Fig. 7A In the configuration shown, the polishing action is concentrated at an annular region 30 of the top surface of the substrate 10 spaced apart from the edge 13 of the substrate.

[0061] As another alternative, the polishing system can use a curved polishing pad that is smaller than the substrate. Fig. 8A and Figure 8B , the curved polishing pad 119" can be held on the bottom of a pad carrier 260 (e.g., a curved metal piece). If the pad carrier 260 remains stationary as the chuck 120 rotates, the polishing action is concentrated at an annular region 30 where the top surface of the substrate 10 is spaced apart from the edge 13 of the substrate. Alternatively, the pad carrier 250 can be fixed at the end of an arm 262 that is rotated by a motor 264 so that the pad carrier 250 and the curved polishing pad 119" orbit around an axis 268 that passes through the center point 15 of the substrate 10.

[0062] Although this specification contains many details, these details should not be construed as limiting the scope of what may be claimed, but rather as descriptions of features specific to a particular example. Certain features described in this specification in the context of separate embodiments may also be combined. Conversely, various features described in the context of a single embodiment may also be implemented separately or in any suitable subcombination in multiple embodiments.

[0063] Similarly, although operations are depicted in a particular order in the accompanying drawings, this should not be understood as requiring that such operations be performed in the particular order shown or in a continuous order, or that all of the operations shown be performed, to achieve the desired result. In some cases, multitasking and parallel processing can be advantageous. In addition, the separation of the various system 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 as a whole can be integrated together in a single software product or packaged into multiple software products.

[0064] A number of embodiments have been described. Nevertheless, it will be appreciated that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A chemical mechanical polishing system, comprising: a support configured to receive and hold the substrate in a face-up orientation; a polishing article having a polishing surface that is smaller than the exposed surface of the substrate; a port for dispensing a polishing liquid to an interface between the polishing pad and the substrate; one or more actuators for contacting the polishing surface with a first portion of the exposed surface of the substrate and producing relative motion between the substrate and the polishing pad and optically transmissive polymer window; an in-situ optical monitoring system including a light source and a detector, the in-situ optical monitoring system configured to direct a light beam from above the support to impinge on a non-overlapping second portion of the exposed surface of the substrate; as well as A controller is configured to receive a signal from the optical in-situ monitoring system and to modify a polishing parameter based on the signal.

2. The system of claim 1 , wherein the in-situ optical monitoring system comprises an optically transmissive polymer window movable into contact with a non-overlapping second portion of the exposed surface of the substrate, and the in-situ optical monitoring system is configured to direct a light beam through the optically transmissive polymer window and the detector is configured to receive a reflection of the light beam through the optically transmissive polymer window.

3. The system of claim 1, wherein the in-situ optical monitoring system is configured to direct a light beam through air onto the exposed surface of the substrate. 4 . The system of claim 3 , comprising a nozzle coupled to a gas source, the nozzle configured to direct a jet of gas onto the exposed surface of the substrate.

5. The system of claim 1, wherein the in-situ optical monitoring system comprises a barrier and a transparent liquid held by the barrier, and the in-situ optical monitoring system is configured to direct a light beam through the transparent liquid onto the exposed surface of the substrate.

6. The system of claim 1 , wherein the polishing article comprises a roller having a cylindrical polishing surface, and wherein one or more actuators are configured to rotate the cylindrical polishing surface about a first axis parallel to the exposed surface of the substrate, the actuator being configured to direct a light beam through air onto the exposed surface of the substrate.

7. The system of claim 6, wherein the polishing parameter comprises a rotation rate of the roller or an angle of the axis relative to a radius of the substrate.

8. The system of claim 6, wherein the roller has a length greater than its diameter.

9. The system of claim 1, wherein the polishing article comprises a rotatable dish-shaped polishing pad having a planar polishing surface to contact the exposed surface of the substrate.

10. The system of claim 1, wherein the polishing article comprises a curved polishing pad having a flat polishing surface to contact the exposed surface of the substrate.

11. The system of claim 1 , wherein the one or more actuators include a first actuator for radially moving the window across the substrate.

12. The system of claim 11, wherein the one or more actuators include a second actuator for rotating the support and the substrate.

13. The system of claim 1, wherein the polishing parameters include one or more of polishing surface pressure, lateral position, or polishing endpoint.

14. The system of claim 1, wherein the light beam impinges on the substrate normal to the exposed surface.

15. The system of claim 1, wherein the polishing article comprises a polymer matrix polishing layer having pores and the window comprises the polymer matrix without pores.

16. A polishing method comprising: contacting a first portion of an exposed surface of a substrate with a polishing surface of a polishing article, wherein the first portion is smaller than the exposed surface of the substrate; supplying a polishing liquid to an interface between the polishing pad and the substrate; generating a signal from an in-situ monitoring system that directs a light beam to a non-overlapping second portion of the exposed surface of the substrate and receives a reflection of the light beam from the substrate; causing relative movement between the substrate and the polishing surface while pressing the polishing surface against the exposed surface of the substrate; as well as Polishing parameters are modified based on the signal.

17. The method of claim 16, comprising: An optically transmissive polymer window of an in-situ optical monitoring system is brought into contact with the exposed surface of the substrate, and the light beam is directed through the window to impinge on the substrate.

18. The method of claim 16, comprising: The light beam is directed through air onto the exposed surface of the substrate.

19. The system of claim 18, comprising: A jet of gas is directed from a nozzle onto the substrate to remove the polishing liquid from the second portion of the substrate.

20. The method of claim 16, comprising: The light beam is directed through a transparent liquid retained by a barrier onto the exposed surface of the substrate.

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