Thickness Monitoring in Face-Up Polishing

Abstract

A chemical mechanical polishing system includes a support configured to receive and hold a substrate face-up, a polishing article having a polishing surface smaller than the exposed surface of the substrate, a port for dispensing a polishing liquid, one or more actuators for contacting the polishing surface with a first portion of the exposed surface of the substrate and for generating relative motion between the substrate, the polishing pad, and a light-transmissive polymer window, an in-situ optical monitor system, and a controller configured to receive signals from the optical in-situ monitor system and to modify polishing parameters based on the signals. The in-situ optical monitor system includes a light source and a detector, and the in-situ optical monitor system is configured to direct a light beam from above the support to impinge on a second, non-overlapping 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 more particularly to layer thickness monitoring in face-up polishing.

Background Art

[0002] Integrated circuits are typically formed on a substrate by continuously depositing conductive, semiconductor, or insulating layers on a silicon wafer. Some manufacturing processes involve depositing a fill layer on an uneven surface and planarizing the fill layer. In some applications, the fill layer is planarized until the top surface of the patterned layer is exposed. A conductive fill layer can be deposited, for example, on a patterned insulating layer to fill trenches or holes in the insulating layer. After planarization, the portions of the metal layer remaining between the raised insulating layer patterns form vias, plugs, and lines that serve as conductive paths between thin film circuits on the substrate. In other applications, such as oxide polishing, the fill layer is planarized by polishing for a predetermined time, for example, leaving a portion of the fill layer on the uneven surface. Further, photolithography typically requires planarization of the substrate surface.

[0003] Chemical mechanical polishing (CMP) is one of the recognized methods of planarization. In this planarization method, it is usually necessary to attach the substrate to a carrier or a polishing head. The exposed surface of the substrate is usually placed in a "face-down" orientation with respect to the rotating polishing pad. The carrier head applies a controllable load by one or more pressure actuators to press the substrate against the polishing pad. A polishing slurry for grinding is usually supplied to the surface of the polishing pad.

[0004] To correct for radial thickness variations caused by either incoming substrate variations or polishing rate variations introduced by the polishing apparatus, a sensor can scan across the substrate during polishing, and a chamber disposed radially within the carrier head can be driven to different pressures.

Summary of the Invention

[0005] Disclosed herein are systems and methods for monitoring the thickness value of an exposed layer of a substrate in “face-up” chemical mechanical polishing. The substrate is disposed on a vacuum support such that the surface of the substrate to be planarized is exposed and in contact with a rotating polishing article. The polishing article is brought into contact with the exposed surface and rotated to polish a portion of the exposed surface.

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

[0007] In one aspect, a chemical mechanical polishing system includes a support configured to receive and hold the substrate in a face-up orientation, a polishing article having a polishing surface smaller than the exposed surface of the substrate, a port for dispensing a polishing liquid at 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 for generating relative motion between the substrate, the polishing pad, and a light-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 polishing parameters 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 irradiate a light beam from above the support and direct it to impinge on 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 that includes a support configured to receive and hold a substrate, a polishing article having a polishing surface smaller than the exposed surface of the substrate, a port for dispensing a polishing liquid at an interface between the polishing pad and the substrate, an in-situ optical monitoring system, and one or more actuators configured to receive signals from the optical in-situ monitoring system and to modify polishing parameters based on the signals. The in-situ optical monitoring system includes a light source, a detector, and a light-transmissive polymer window. The light source is configured to direct a light beam through the light-transmissive polymer window, and the detector is configured to receive a reflection of the light beam through the light-transmissive polymer window. The one or more actuators are configured to contact the polishing surface to a first portion of the exposed surface of the substrate, to contact the light-transmissive polymer window to a non-overlapping second portion of the exposed surface of the substrate, and to generate relative movement between the substrate, the polishing pad, and the light-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 smaller than the exposed surface of the substrate, a port for dispensing a polishing liquid at an interface between the polishing pad and the substrate, an in-situ optical monitoring system, and one or more actuators configured to receive signals from the optical in-situ monitoring system and modify polishing parameters based on the signals. The in-situ optical monitoring system includes a light source, a detector, and a light-transmissive polymer window. The light source is configured to direct a light beam directly onto the substrate, through the light-transmissive polymer window, and through a water column in contact with the substrate. The detector is configured to receive reflections of the light beam directly from the substrate, through the light-transmissive polymer window, or through the water column in contact with the substrate. The one or more actuators are configured to bring the polishing surface into contact with a first portion of the exposed surface of the substrate, move the in-situ optical monitoring system above a second portion of the exposed surface of the substrate that does not overlap the first portion, and generate relative movement between the substrate, the polishing pad, and the in-situ optical monitoring system.

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

[0011] The in-situ monitoring system may include one or more optical fibers for carrying light from a light source to a window and for carrying reflected light reflected from a substrate and passing through the window to a detector. A first axis may be substantially perpendicular to a segment extending from a second axis to a center point of a roller. The relative movement may include moving the polishing surface parallel to the plane of the polishing surface. The in-situ monitoring system may be configured to direct a light beam onto an edge portion of the substrate, in which case a cylindrical polishing surface extends across the edge of the substrate. The ends of the cylindrical polishing surface may be spaced radially inwardly from the edge of the substrate. Both ends of the cylindrical polishing surface are located within 40 mm from the edge of the substrate. Based on the received reflected signal, the angular orientation of the substrate can be determined. The controller may be configured to determine the thickness of the uppermost layer of the substrate or the thickness profile of the uppermost layer of the substrate.

[0012] Certain embodiments of the subject matter described herein may be implemented to realize one or more of the following technical advantages. Wafer-to-wafer (WTW) and within-wafer (WIW) polishing uniformity can be improved. Non-uniformities in both the radial and angular directions can be reduced. By determining the polishing parameters of the polishing operation, it becomes easier to instruct the polishing operation to achieve a desired polishing profile. This polishing profile can be supplied to an algorithm for improving material removal accuracy.

[0013] Details of one or more embodiments are set forth in the accompanying drawings and the following description. Other features and advantages will be apparent from the description and drawings and from the claims.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

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Figure 7A

Figure 7B

Figure 8A

Figure 8B

DETAILED DESCRIPTION OF THE INVENTION

[0015] In the figures, like reference numerals indicate like elements.

[0016] In the manufacturing process of semiconductor chips, in addition to the radial thickness variation, there is also an angular thickness variation that depends on, for example, the azimuth angle centered on the center of the substrate. Similar to the radial variation, the angular variation may be caused by the variation of the incoming substrate or may be caused by the variation of the polishing rate induced by the polishing apparatus. Various "touch-up" polishing processes have been proposed, such as using a rotating small disk-shaped polishing pad. However, such "touch-up" polishing processes contact the substrate in a narrow area, resulting in low throughput. "Touch-up" polishing is sometimes called local site polishing (LSP).

[0017] This specification describes a location-specific polishing method that uses data collected in real time from the exposed surface of a substrate, measured by an in-situ optical monitoring system. The system controller receives data indicating the thickness of the layers of the exposed surface and modifies one or more polishing parameters to achieve a target thickness profile.

[0018] Parameters of the polishing roller, such as roller diameter, grit of the pad, etc., can be selected based on the shape and / or thickness profile of the substrate, thus providing flexibility for various polishing processes. Furthermore, the polishing roller can be purchased off-the-shelf or 3D printed, thereby reducing costs and minimizing the downtime of equipment for maintenance. The controller functions to optimize the rotational speed of the substrate, the rotational speed and pressure of the polishing roller, the orientation of the roller, and the scanning profile of the roller to achieve precise location-specific material removal.

[0019] Referring to FIGS. 1 and 2, FIG. 1 shows an example of a polishing system 100, and FIG. 2 shows a perspective view of an exemplary polishing system 100. The polishing system 100 includes a rotatable disk-shaped chuck 120 on which a substrate 10 is placed. As an installed system, the chuck 120 holds the substrate in a "face-up" orientation, i.e., the flat upper surface 12 to be polished is substantially perpendicular to gravity and is oriented such that the polishing liquid dispensed onto the upper surface 12 is supported by the upper surface 12 (however, the polishing liquid can be flung off by the rotation of the substrate 10).

[0020] The chuck 120 is operable to rotate about the rotation axis 125. For example, an actuator, such as a motor 121, such as a DC induction motor, can rotate the drive shaft 124 to rotate the chuck 120. During operation, the substrate 10 is held on the upper surface of the chuck 120 by a vacuum applied to the lower surface 14 of the substrate 10 by, for example, a vacuum source 112, such as 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 of the substrate 10, such as the upper surface, to the polishing system 100 without interfering with the polishing process.

[0021] The polishing system 100 includes a first actuator operable to rotate the rotating drum 118 about the main rotation axis 162 (see FIG. 2, this axis extends out of the paper plane in FIG. 1). A polishing layer 119 is attached to at least a part of the cylindrical outer peripheral surface of the drum 118, thus forming a cylindrical polishing surface 119a. The drum 118 and the attached polishing layer 119 constitute a polishing roller 160. The drum 118 in FIG. 1 is cylindrical with a length longer than the diameter. The main rotation axis 162 is coaxial with the longitudinal axis of the roller 160. The roller 160 is arranged such that this main axis is parallel to the front surface of the substrate 10, such as the exposed upper surface. Further, the rotation axis 162 can be perpendicular to the radial segment 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.

[0022] 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 can include one or more layers. The outermost layer of the polishing layer 119 is a polishing layer. The material of the polishing layer can be a polymer, such as polyurethane, and can be a micro-porous layer, such as IC1000 polishing layer material.

[0023] The polishing system 100 can include a port 130 for dispensing a polishing liquid 132, such as a grinding slurry, onto the polishing substrate 10. The polishing liquid 132 will be carried under the roller 160 on the substrate 10 by the rotation of the chuck 120 and the substrate 10. Alternatively, the port can directly dispense the polishing liquid onto the roller 160.

[0024] 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 to release the contact between the polishing surface of the roller 160 and the surface of the substrate 10. During the polishing operation, the roller 160 is brought into contact with the front surface of the substrate 10 to create a contact area between the polishing surface of the roller 160 and the front surface of the substrate 10. The polishing system 100 commands the second actuator to apply a force to the roller 160 in a direction orthogonal to the exposed surface, for example, toward the substrate 10, such that the roller 160 is pressed. The force applied to the contact area via the roller 160 can be in the range of 0.5 to 5 psi.

[0025] Due to the rotational movement of the polishing surface of the roller 160 in the presence of the polishing liquid 132, a portion of the material of the substrate 10 within the contact area is removed, for example, polished, while the material of the substrate 10 outside the contact area is not removed. Optionally, the roller 160 can be moved along an axis parallel to the plane of the substrate 10, for example, from right to left in FIG. 1, to relocate the contact area along the front surface of the substrate 10. Due to the rotation of the substrate 10 and the rotational and translational movements of the roller 160, a relative movement occurs between the roller 160 and the front surface of the substrate 10. While in contact with the substrate 10, the rotational speed of the roller 160 can be in the range of 10 rpm to 2500 rpm (for example, 50 rpm to 1500 rpm).

[0026] The time during which the roller 160 is in contact with the substrate 10 is the contact time. The time the roller stays on any particular area, together with the pressure and the rotational speed, determines the amount of material removed from the substrate. After the lapse of the contact time between the roller 160 and the substrate 10, the contact between the roller 160 and the substrate 10 can be released to stop the polishing.

[0027] For example, to correct for asymmetry, the azimuthal polishing profile can be controlled by synchronizing the pressure or position of the roller with the rotation of the chuck (at a low chuck speed).

[0028] To control the rotational speed of the chuck 120, a controller 190, such as a programmable computer, is connected to the motor 121. For example, the motor 121 may include an encoder that measures the rotational speed of the associated drive shaft. The feedback control circuit may be within the motor 121 itself, part of the controller 190, or a separate circuit, and receives the rotational speed measured from the encoder and adjusts the current supplied to the motor 121 so that the rotational speed of the drive shaft is guaranteed to match the rotational speed received from the controller 190.

[0029] The system 100 includes a position sensor 140 for sensing the angular position of the chuck 120 or the substrate 10. This enables the orientation of the substrate 10 with respect to the chuck 120, the orientation with respect to the polishing profile stored in the controller 190, or both.

[0030] For example, the position sensor can be an optical sensor disposed near the edge of the chuck 120, and this sensor is adapted to overlap the annular edge of the substrate. The substrate 10 may include a notch 142 (see FIG. 2) or a flat portion (see FIGS. 3A and 3B). Thus, as the substrate 10 rotates together with the chuck 120, the position sensor 140 intermittently passes over the notch 142 or the flat portion, and as a result, the reflectivity optically detected by the sensor 140 changes. As another example, the optical sensor 140 can be an optical interrupter. In particular, 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 intermittently passes between the light source and the detector, blocking the light beam, and this is optically detected by the sensor. The rotational speed of the chuck and the substrate 10 can be obtained from the frequency of detection of the notch or the detection of light interruption.

[0031] The polishing system 100 includes an in-situ optical monitoring system 180 for measuring a signal indicating the thickness of the exposed layer on the surface of the substrate 10. The optical monitoring system 180 includes a light source 182 and a sensor 184 connected to a light-transmissive window 150. During operation, the window 150 is physically contacted with the upper surface 12 of the substrate 10.

[0032] The light source 182 generates light, and this light is transmitted to the window 150 by connection with an optical fiber 186, such as an optical fiber cable. In some implementations, the light source 182 is a laser, a flash lamp, or a discharge lamp. In one example, the light is a broad spectrum over visible wavelengths, such as white light. In an alternative example, the light has a bandwidth including a portion of the visible wavelength, such as a bandwidth of 10 nm or a bandwidth of 100 nm. The light source 182 may include filters, mirrors, or diffraction gratings necessary to generate light of a selected spectrum or bandwidth.

[0033] Window 150 is made of a transmissive material that has, for example, at least 90%, at least 95%, or at least 99% transmissivity with respect to the wavelength monitored by the detector and is chemically compatible with the polishing process. Window 150 has sufficient durability to withstand the frictional forces generated by the contact between window 150, substrate 10, and polishing liquid 132. 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 (PET), or amorphous copolyester (PETG). In some implementations, window 150 is formed with the same polymer composition as the polishing layer of polishing layer 119 on drum 118. In some implementations, the polishing layer of polishing layer 119 is a polymer matrix having pores, for example, liquid-filled pores or hollow microspheres, while window 150 is formed of the same polymer matrix but has no pores. In some implementations, window 150 and the matrix material of polishing layer 119 use the same two (or more) monomer or polymer components, but their weight percentage contributions are different so as to obtain different compressibilities.

[0034] Window 150 contacts the upper surface of substrate 10. Light forms light beam 152, which is transmitted through window 150, reflected from the upper surface of substrate 10, and this reflection is sent 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. In this configuration, light beam 152 impinges the substrate 10 normal to the exposed surface 12. Optical sensor 184 can be a spectrometer.

[0035] Sensor 184 receives the reflected light from window 150, and optical monitoring system 180 determines a thickness profile indicating the thickness of the layer of the substrate under window 150 based on the signal from sensor 184. Controller 190 can store the target thickness profile of the layer of substrate 10 to be polished.

[0036] Referring again to FIGS. 1 and 2, during the polishing operation, the contact time, the rotational speed and the translational speed of roller 160, and the pressure parameters can be determined based on the amount of material to be removed so as to achieve the target thickness profile and constitute a correction profile. The correction profile can be loaded into the controller of polishing system 100 to control the chuck 110, roller 160, and the flow rate of liquid 132. For example, controller 190 controls the polishing parameters of the polishing operation so as to achieve the target thickness profile. Some examples of polishing parameters include the rotational speed (e.g., of chuck 120 or roller 160), the pressure (e.g., of roller 160), the contact time, the translational speed, the orientation angle, or the polishing area (e.g., annular area 30). Specific examples of polishing parameters include one or more of the pressure of the polishing pad against the substrate, the lateral position of the polishing surface relative to the substrate, the movement speed of the polishing surface relative to the substrate, the polishing end point, the rotational speed of the roller, or the angle of the main axis relative to the radius of the substrate.

[0037] Referring to FIG. 3A, the main axis of roller 160 can be oriented at any angle within the range from 0° (e.g., parallel) to 90° (e.g., perpendicular) with respect to the line (e.g., line segment) connecting the center point 15 of substrate 10 and the center point 126 of roller 160. For example, the main axis of roller 160 in FIG. 4A is oriented perpendicular (e.g., 90° therefrom) to the line connecting the center point 15 of substrate 10 and the center point 134 of roller 160.

[0038] The edge of the roller 160 is disposed at or near the edge 13 of the substrate 10, or, for example, 1 to 30 mm radially inward from the edge 13. In some implementations, the roller 160 is substantially perpendicular (e.g., 80 - 90°) to the line connecting the substrate center point 15 and 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 in the annular region 30 of the upper surface of the substrate 10 disposed at a distance from the substrate edge 13. In other words, the portion of the substrate that contacts the roller 160 and is rotated about the center point 15 forms the annular region 30. The central region 34 radially inward of the annular region 30 and the second annular region 36 surrounding the polished annular region 30 are not polished.

[0039] FIG. 3B shows a top view of the substrate 10 during the polishing operation in which the window 150 is moved in the direction indicated by the double arrows adjacent to the window 150 of FIG. 3B. In some implementations, the direction is radial, such as between a point on the edge 13 and the center point 15. As the substrate 10 is rotated with the chuck 120 in the direction of motion 16, the window 150 follows a spiral path 38 toward the center point 15. The dimensions of the window 150 determine the portion of the substrate 10 covered by the window 150 as it follows the path 38. The portion where the window 150 contacts does not overlap with the portion where the roller 160 contacts.

[0040] Next, referring to FIG. 4, a flowchart diagram showing an overview of the steps of a method 400 for polishing a substrate is shown. The method 400 includes the following steps.

[0041] The method includes contacting the surface of the substrate 10 with the roller 160 (step 402). The polishing surface of the roller 160 rotates about a main rotation axis parallel to the surface to be polished.

[0042] The method includes supplying a polishing liquid 132 to the interface between the roller 160 and the substrate 10 (step 404). Examples of the polishing liquid 132 include a carrier fluid in which abrasive particles are suspended, such as a grinding slurry. The port 130 of the system 100 dispenses the liquid 132 onto the polishing surface of the substrate 10.

[0043] The method includes contacting window 150 of in-situ optical monitor system 180 with the surface of the substrate (step 406). In some implementations, detector 184 of optical monitor system 180 is optically coupled to transparent optical window 150 via a light transmissive connection such as an optical fiber cable.

[0044] The method includes causing relative motion between substrate 10 and roller 160 (step 408). Relative motion can also be caused between substrate 10 and window 150. Examples of relative motion include rotating the polishing surface of roller 160 about the main axis while pressing the polishing surface against the exposed front surface of substrate 10. Additionally or alternatively, rotating chuck 120 that supports substrate 10 causes relative motion between substrate 10 and both roller 160 and window 150. Relative motion between substrate 10 and window 150 can also occur by sweeping the window transversely across substrate 10, e.g., in a radial direction. Coupling this transverse motion with the rotation of chuck 120 can generate a helical sweep of window 150 across substrate 10.

[0045] The method includes monitoring a signal from in-situ optical monitor system 180 (step 410). Light source 182 generates light that is transmitted to window 150. The light reflects off the exposed surface of substrate 10 in contact with window 150. The reflected light is captured by detector 184 or alternatively by an optical fiber connection that connects window 150 to detector 184. Optical monitor system 180 generates a thickness signal based on the reflected light. Alternatively, optical monitor system 180 transmits a measurement of the reflected light to system controller 105, and system controller 105 generates the thickness signal. Since window 150 sweeps transversely across substrate 10, the system can generate a thickness profile, e.g., a radial thickness profile.

[0046] The method includes modifying the polishing parameters (step 412) based on the measured thickness profile meeting the desired polishing criteria. The system controller 105 receives the measured thickness profile and compares the measured thickness profile to a target profile. If the difference between the measured thickness profile and the target profile exceeds a threshold, the system controller 105 can change one or more polishing parameters, such as the position or rotational speed of the roller, to correct it. Alternatively or additionally, the system controller 105 can interrupt the polishing when the measured thickness profile matches the target thickness profile.

[0047] In the above description, the focus was on the window that contacts the substrate, but several other techniques can be used.

[0048] For example, the light beam is transmitted through a "water column" to the substrate surface. Referring to FIG. 5, a barrier 200 having an aperture 202 can be placed in contact with the exposed surface 12 of the substrate 10. A transparent liquid 210, such as water, is placed in the aperture 202 to form a "water column" of the transparent liquid that contacts the exposed surface 12 of the substrate 10. The barrier 200 can hold the transparent liquid 210 to obtain 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 such that the light beam 152 passes through the transparent liquid 210 of the "water column" and is incident on the substrate and reflected back from the substrate. In this case, step 406 shown in FIG. 4 would include contacting the water column with the surface of the substrate.

[0049] As another example, a slurry can be blown off the exposed surface of the substrate with a gas jet. Referring to FIG. 6, a nozzle 220 is disposed above the substrate. To form a gas jet 222, a gas, such as pure air or nitrogen gas, is introduced through the nozzle 220. The nozzle 220 is arranged such that the gas jet 222 blows off any polishing liquid 132 from the substrate in the region 224 where the light beam 152 is incident on the exposed surface of the substrate 10. This can prevent the polishing liquid, such as abrasive particles in the polishing liquid, from scattering a part of the light beam and generating noise in the measurement signal. The detector of the in-situ monitoring system that is in contact with the surface of the substrate. In this case, step 406 shown in FIG. 4 will be replaced with the step of blowing off the polishing liquid from the surface of the substrate.

[0050] Furthermore, in the above description, the focus has been on a roller having a cylindrical polishing layer. However, the optical monitoring techniques discussed above with respect to FIGS. 1, 5, and 6 can also be used with other polishing layer configurations.

[0051] For example, the polishing system can use a rotatable circular disk-shaped polishing pad that is smaller than the substrate. Referring to FIGS. 7A and 7B, a circular polishing layer 119', i.e., the polishing pad, can be held at the bottom of a pad carrier 250, such as a metal disk. The pad 119' contacts only a part of the substrate 10. In some implementations, 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 passing through the center of the polishing pad 119'. In some implementations, the axis 256 is slightly offset from the center of the polishing pad 119' such that the pad performs a circular motion on the substrate. In either case, due to the rotation of the chuck 120, in the configuration shown in FIG. 7A, the polishing action is concentrated in the annular region 30 on the upper surface of the substrate 10 disposed at an interval from the substrate edge 13.

[0052] Alternatively, the polishing system can use an arcuate polishing pad that is smaller than the substrate. Referring to FIGS. 8A and 8B, the arcuate polishing pad 119” can be held on the bottom of a pad carrier 260, such as an arcuate metal piece. When the pad carrier 260 is held stationary during rotation of the chuck 120, the polishing action is concentrated on the annular region 30 of the upper surface of the substrate 10 that is spaced from the substrate edge 13. Alternatively, the pad carrier 250 and the arcuate polishing pad 119” can be attached to the end of an arm 262 that is rotated by a motor 264 so as to revolve about an axis 268 passing through the center point 15 of the substrate 10.

[0053] Although this specification contains many details, these should not be construed as limiting the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Certain features that are described in this specification in the context of separate implementations can also be combined. Conversely, the various features described in the context of a single implementation can also be implemented separately, or in any suitable sub-combination, in multiple implementations.

[0054] Similarly, although operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or continuously, or that all of the operations shown be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Further, the separation of various system components in the above-described implementations should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can be integrated entirely as a single software product, or packaged into multiple software products.

[0055] Some implementations have been described. However, it will be understood that various modifications can be made without departing from the spirit and scope of the present invention. Therefore, other implementations exist within the scope of the following claims.

Claims

1. a support configured to receive and hold a substrate in a face-up orientation; a polishing article having a polishing surface smaller than the exposed surface of the substrate; a port for dispensing a polishing liquid at 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 for generating relative movement between the substrate, the polishing pad, and a light-transmissive polymer window; an in-situ optical monitoring system including a light source and a detector, the in-situ optical monitoring system being configured to direct a light beam from above the support to impinge on a second portion of the exposed surface of the substrate that does not overlap the first portion; a controller configured to receive a signal from the optical in-situ monitoring system and to modify polishing parameters based on the signal A chemical mechanical polishing system comprising.

2. The in-situ optical monitoring system includes a light-transmissive polymer window movable to contact a second portion of the exposed surface of the substrate that does not overlap the first portion, the in-situ optical monitoring system being configured to direct a light beam through the light-transmissive polymer window, and the detector being configured to receive a reflection of the light beam through the light-transmissive polymer window. The system according to claim 1.

3. The in-situ optical monitoring system according to claim 1, wherein the in-situ optical monitoring system is configured to direct a light beam onto the exposed surface of the substrate through air.

4. The system according to claim 3, further comprising a nozzle coupled to a gas source, the nozzle being configured to direct a jet of gas onto the exposed surface of the substrate.

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

6. The system according to claim 1, wherein the polishing article includes a roller having a cylindrical polishing surface, and the one or more actuators are configured to rotate the cylindrical polishing surface about a first axis parallel to the exposed surface of the substrate.

7. The system according to claim 6, wherein the polishing parameters include the rotational speed of the roller or the angle of the axis with respect to the radius of the substrate.

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

9. The system according to claim 1, wherein the polishing article comprises a rotatable disk-shaped polishing pad having a flat polishing surface that contacts the exposed surface of the substrate.

10. The system according to claim 1, wherein the polishing article comprises an arc-shaped polishing pad having a flat polishing surface that contacts the exposed surface of the substrate.

11. The system according to claim 1, wherein the one or more actuators comprise a first actuator for moving the window so as to move in the radial direction of the substrate.

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

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

14. The system according to claim 1, wherein the light beam is incident on the substrate and is incident in a direction normal to the exposed surface.

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

16. Contacting a first portion of the exposed surface of the substrate with the polishing surface of the polishing article, wherein the first portion is smaller than the exposed surface of the substrate; Supplying a polishing liquid to the interface between the polishing pad and the substrate; Directing a light beam onto a second portion of the exposed surface of the substrate that does not overlap the first portion and generating a signal from an in-situ monitoring system that receives the 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; Modifying the polishing parameters based on the signal A polishing method comprising:

17. The method according to claim 16, comprising contacting the light-transmissive polymer window of the in-situ optical monitoring system with the exposed surface of the substrate and guiding the light beam through the window to be incident on the substrate.

18. The method according to claim 16, comprising guiding the light beam through air onto the exposed surface of the substrate. **Claim 19** The method according to claim 18, comprising guiding a jet of gas from a nozzle onto the substrate to remove the polishing liquid from the second portion of the substrate. **Claim 20** The method according to claim 16, comprising guiding the light beam through a transparent liquid held by a barrier onto the exposed surface of the substrate.

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