Acoustic Monitoring of the Conditioner during Grinding

Abstract

A chemical mechanical polishing apparatus includes a platen for supporting a polishing pad, a conditioner head for keeping a conditioner disk in contact with the polishing pad, a motor for generating relative movement between the polishing pad and the conditioner disk so as to condition the polishing pad, an in-situ acoustic monitoring system having an acoustic sensor for receiving an acoustic signal from the conditioner disk, and a controller configured to analyze a signal from the acoustic sensor and determine characteristics of the conditioner disk or the conditioner head based on the signal.

Description

Technical Field

[0001] The present disclosure relates to chemical mechanical polishing, and more particularly, to acoustic monitoring during chemical mechanical polishing.

Background Art

[0002] Integrated circuits are generally formed on a substrate by successive deposition of conductive, semiconductive, or insulating layers on a silicon wafer. One manufacturing step involves depositing a fill layer on a non-planar surface and planarizing the fill layer. In some applications, the fill layer is planarized until the top surface of the patterned layer is exposed. For example, a conductive fill layer can be deposited on a patterned insulating layer to fill trenches or holes in the insulating layer. After planarization, the portions of the conductive layer remaining between the raised patterns of the insulating layer form vias, plugs, and lines that provide conductive paths between thin film circuits on the substrate. In other applications, such as oxide polishing, the fill layer is planarized until a predetermined thickness remains on the non-planar surface. Additionally, planarization of the substrate surface is typically required for photolithography.

[0003] Chemical mechanical polishing (CMP) is an accepted method of planarization. This planarization method generally requires that the substrate be mounted on a carrier head or polishing head. The exposed surface of the substrate is generally placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to press the substrate against the polishing pad. An abrasive polishing slurry is generally applied to the surface of the polishing pad.

[0004] When the polisher is operating, the pad is subject to compression, shear, and friction, which result in heat and wear. Slurry and abraded material from the wafer and pad are pressed into the pores of the pad material, and the material itself becomes matted and even partially dissolved. These effects, sometimes referred to as "glazing," reduce the pad roughness and its ability to apply fresh slurry to the substrate. Therefore, it is desirable to condition the pad by removing the captured slurry and unmatting, re-inflating, or re-roughening the pad material.

[0005] A polishing system generally includes a conditioner system for conditioning the polishing pad. Conditioning the polishing pad maintains a consistent roughness of the polishing surface to ensure uniform polishing conditions for each wafer. Conventional conditioner systems have a conditioner head that holds a conditioner disk with an abrasive lower surface, for example, with diamond particles, and the conditioner disk is placed in contact with the polishing pad. The contact and movement of the abrasive surface against the polishing pad roughens the polishing surface. However, the conditioner disk itself is subject to wear and needs to be replaced periodically. SUMMARY OF THE INVENTION

[0006] In one aspect, a chemical mechanical polishing apparatus includes a platen for supporting a polishing pad, a conditioner head for holding a conditioner disk in contact with the polishing pad, a motor for generating relative movement between the polishing pad and the conditioner disk to condition the polishing pad, an in-situ acoustic monitoring system having an acoustic sensor for receiving an acoustic signal from the conditioner disk, and a controller configured to analyze a signal from the acoustic sensor and determine a characteristic of the conditioner disk or the conditioner head based on the signal.

[0007] One or more of the following possible advantages may be realized.

[0008] Wear of the conditioning disk can be monitored in situ, and the end-of-life of the conditioner disk can be detected in situ and more reliably. When the end-of-life of the conditioner is detected, an alert can be generated to trigger replacement of the conditioner disk. The risk of substrate defects or scratching can be reduced. The effective lifetime of the conditioner disk can be improved, and the downtime for replacement of the conditioner disk can be reduced, thus improving the cost of ownership. Other anomalies associated with the conditioner can be detected, and an alert can be generated to trigger a corrective action. For example, improper installation of the conditioner disk or inaccurate conditioning downforce can be detected.

[0009] 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

[0010]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0011] In the figures, like reference numerals indicate like elements.

[0012] The chemical mechanical polishing process can include a pad conditioning step of pressing a conditioner disk, e.g., a disk coated with abrasive diamond particles, against a rotating polishing pad to condition and texture the polishing pad surface. However, the friction of the pad against the abrasive particles of the conditioner disk and / or the chemical action of the polishing liquid may gradually wear the conditioner disk. For example, the abrasive particles may become blunt and reduce the wear rate, or the abrasive particles may be released from the conditioner disk, causing scratching and defects on the substrate. Therefore, the conditioning disk needs to be replaced regularly. However, due to simple manufacturing variations, conditioning disks do not all have the same service life.

[0013] One approach is simply to replace the conditioning disk after a set interval, e.g., after a preset number of polishes of the substrate, or after a preset usage time. However, this poses the risk of both underusing the conditioning disk, i.e., replacing a disk that still has useful life, or overusing it, which risks damage to the substrate. Another approach is to monitor the wear of the polishing pad, and a change in the wear rate can indicate problems with the conditioner disk. However, this is an indirect indication, and the conditioner disk can experience wear and the risk of detachment of abrasive particles without a change in the wear rate.

[0014] Monitoring of the acoustic signal from the conditioner disk can address these issues and can be a more reliable technique for detecting when the conditioner disk needs to be replaced. Even without monitoring the conditioner disk lifetime, acoustic monitoring can provide indications of other anomalies and enable corrective actions to be taken by the operator of the polishing system.

[0015] As shown in FIGS. 1 and 2A, the chemical mechanical polishing system 20 includes a rotatable platen 24 with a polishing pad 30 thereon. The platen 24 is operable to rotate about an axis 25 (see arrow A in FIG. 2A). For example, a motor 22 can rotate a drive shaft 28 to rotate the platen 24. The polishing pad 30 can be a two-layer polishing pad having an outer polishing layer 34 with a polishing surface 36 and a softer backing layer 32.

[0016] The polishing system 20 includes a supply port 64, for example, at the end of a slurry supply arm 62, for dispensing a polishing fluid 60, such as a polishing abrasive slurry, onto the polishing pad 30. In some implementations, the polishing system 20 includes a wiper blade or body for uniformly distributing the polishing fluid 60 across the polishing pad 30.

[0017] The carrier head 70 is suspended from a support structure 72, such as a carousel or track, and is connected by a drive shaft 74 to a carrier head rotation motor 76 so that the carrier head can rotate about an axis 71 (see arrow B in FIG. 2A). Optionally, the carrier head 70 can vibrate laterally, for example, on a slider on a carousel or track 72 or by the rotational vibration of the carousel itself (see arrow C in FIG. 2A). During operation, the platen is rotated about its central axis 25, the carrier head is rotated about its central axis 71, and is translated laterally across the upper surface of the polishing pad 30. The carrier head 70 can include a flexible membrane 80 having a substrate mounting surface for contacting the back side of the substrate 10, and a plurality of pressurizable chambers 82 for applying different pressures to different zones on the substrate 10, such as different radially oriented zones. For ease of explanation, three chambers are shown in FIG. 1, but there can be one or two chambers, or four or more chambers, such as five chambers. The carrier head 70 can also include a retaining ring 84 for holding the substrate below the membrane 80.

[0018] A controller 90, such as a programmable computer, is connected to motors 121, 154 to control the rotation rates of the platen 120 and the carrier head 140. For example, each motor can include an encoder that measures the rotation rate of the associated drive shaft.

[0019] The polishing station 20 also includes a pad conditioner 40 having a conditioner disk 50 for maintaining the surface roughness of the polishing pad 30. The bottom surface of the conditioner disk 50 includes one or more abrasive regions 52 that contact the polishing surface 36 during the conditioning process. The abrasive regions can be provided by abrasive diamond particles fixed to the lower surface of a backing plate 54. The backing plate 54 is generally a metal such as stainless steel, but other materials such as ceramics are possible. In some implementations, other compositions, such as abrasive particles of silicon carbide, are used instead of or in addition to the diamond particles.

[0020] During conditioning, the abrasive regions move relative to the surface of the polishing pad 30, thereby abrading and re-texturing the polishing surface 36. For example, both the polishing pad 30 and the conditioning disk 50 can rotate (see arrows A and D in FIG. 2A).

[0021] The conditioner disk 50 can be held by a conditioner head 46 at the end of an arm 42. The arm 42 and the conditioner head 46 are supported by a base 48. The arm 42 can oscillate to sweep the conditioner head 46 and the conditioner disk 50 laterally across the polishing pad 30 (see arrow E in FIG. 2A). For example, the base 48 is driven by a motor 49 to pivot about a vertical axis, thereby enabling the arm 42 and the conditioner head 46 to sweep laterally over the platen 24 and the polishing pad 30.

[0022] The conditioner head 46 includes a mechanism for attaching the conditioner disk 50 to the conditioner head 46 (such as a mechanical attachment system, for example, bolts or screws, or a magnetic attachment system), and a mechanism for rotating the conditioner disk 50 about the axis 41 (such as a drive belt passing through an arm, or a rotor within the conditioner head). Further, the pad conditioner 40 can also include a mechanism for adjusting the pressure between the conditioner disk 50 and the polishing pad 30 (such as a pneumatic or mechanical actuator within the conditioning head or base), and / or a mechanism for changing the vertical position of the conditioner disk 50 relative to the polishing pad 30. For example, the conditioner head 46 can include an upper portion 46a, a lower portion 46b that holds the conditioner disk 50, and an actuator for adjusting the vertical position of the lower portion 46b relative to the upper portion 46a or for adjusting the pressure of the conditioner disk 50 against the polishing pad 30. However, these mechanisms can have many possible implementations (and are not limited to those shown in FIG. 1). As another example, a vertical actuator can be disposed within the base 48 to lift and lower the arm 42, or the arm can be pivotally attached to the base 48 in a manner that allows the arm to swing vertically to lower and lift the conditioner head 46 from the polishing pad 30.

[0023] The polishing system 20 includes at least one in-situ acoustic monitoring system 100. The in-situ acoustic monitoring system 100 includes an acoustic sensor 102. In the implementation shown in FIG. 1, the acoustic sensor 102 is located on the side of the substrate 10 farther from the polishing pad 30 and will receive an acoustic signal through the polishing pad 30 from the substrate conditioner disk 50. In particular, the acoustic sensor 102 can be supported on the platen 24. For example, the acoustic sensor 102 can be located in a recess 28 in the platen 24. In some implementations, the upper surface of the acoustic sensor 102 is in the same plane as the upper surface of the platen 24.

[0024] The acoustic sensor 102 is positioned on the platen 24 at a radial position (from the axis 25) such that, for at least some lateral positions of the conditioner head 46, the sensor 102 sweeps below the conditioner disk 50. For example, the acoustic sensor 102 can be disposed at an intermediate point between the edge of the platen 24 and the axis of rotation 25.

[0025] In some implementations, the portion of the polishing pad immediately above the acoustic sensor 102 can include an acoustic window 120, e.g., a region having a lower acoustic impedance than the surrounding polishing material. The acoustic window 120 can extend through the polishing layer 32, or the backing layer 34, or both. However, if the acoustic transmission of the polishing pad is high enough, the acoustic window 120 may not be necessary.

[0026] The acoustic sensor 102 can be a contact acoustic sensor having a surface that is connected to (e.g., in direct contact with, or having only an adhesive layer for attachment thereto, or having only an acoustic gel for transmission of an acoustic signal therefrom) a portion of the polishing pad, e.g., the polishing layer 32, or the backing layer 34, or the acoustic window 120. For example, the acoustic sensor 102 can be an electromagnetic acoustic transducer or a piezoelectric acoustic transducer. The piezoelectric sensor can include a rigid contact plate, e.g., made of stainless steel, placed in contact with the body to be monitored, and a piezoelectric assembly on the back side of the contact plate, e.g., a piezoelectric layer sandwiched between two electrodes.

[0027] In some implementations, the spring 106 is positioned to move the acoustic sensor 102 into contact with a portion of the polishing pad 30. In some implementations, the spring 106 is a long travel spring.

[0028] The acoustic sensor 102 can be connected by the circuit 108 to a power supply and / or other signal processing electronics 110 through a rotary joint 112, such as a mercury slip ring. The signal processing electronics 110 can be connected to the controller 90. In some implementations, some or all of the functionality of the signal processing electronics 110 is implemented by the controller 90.

[0029] In some implementations, the in-situ acoustic monitoring system 100 is a passive acoustic monitoring system. In this case, the signal is monitored by the acoustic sensor 102 without generating a signal from an acoustic signal generator (or the acoustic signal generator can be completely omitted from the system). The passive acoustic signal monitored by the acoustic sensor 162 can be in the range of 50 kHz to 1 MHz, for example, 200 to 400 kHz, or within 200 Khz to 1 MHz.

[0030] The signal from the sensor 102 can be amplified by a built-in internal amplifier. In some implementations, the amplification gain is between 40 and 60 dB (for example, 50 dB). The signal from the acoustic sensor 106 can then be further amplified and, if necessary, filtered, and digitized, for example, in the electronics 108 or 110, through an A / D port to a high-speed data acquisition board. The data from the acoustic sensor 102 can be recorded in the range of 1 to 10 MHz, for example, 1 to 3 MHz or 6 to 8 Mz. In implementations where the acoustic sensor 162 is a passive acoustic sensor, a frequency range up to 100 kHz to 2 MHz, such as 500 kHz to 1 MHz (for example, 750 kHz), can be monitored.

[0031] To sense the angular position of the platen 24, a position sensor, for example, an optical interrupter connected to the edge of the platen or a rotary encoder, can be used. This enables only the portion of the signal that is measured when the sensor 102 is close to the conditioner disk 50, for example, when the sensor 102 is below the conditioner disk 50, to be used as indicative of the conditioner disk condition in subsequent signal processing.

[0032] Referring to FIG. 2A, due to the movement of the platen 24 (indicated by arrow A), the acoustic sensor 102 sweeps in a path 200 that travels below the conditioner disk 50. An acoustic monitoring system 100, for example, a controller 90, can be configured to sample the signal from the sensor 102 when the sensor 102 is passing below the conditioner disk 50. For example, the controller 90 can determine the angular position of the sensor 102 based on an input from a motor encoder or a platen position sensor and can compare this, for example, to the position of the conditioner head based on conditioner sweep information. The determination of the position of the sensor relative to the substrate is described in U.S. Patent No. 6,159,073 and in U.S. Patent No. 6,296,548, and equivalent techniques can be applied for a moving conditioner disk. This enables the portion of the signal received when the sensor 102 is below the conditioner disk 50 to be identified and selected.

[0033] Referring to FIGS. 2A and 2B, the signal 220 from the sensor 102 includes a portion 222 corresponding to the sensor 102 that is away from but approaching the conditioner disk 50 (shown by the region 202 of the path 200 and referred to as "leading off-conditioner data"), a portion 224 corresponding to the sensor 102 under the conditioner disk 50 (referred to as "on-conditioner data"), and a portion 222 corresponding to the sensor 102 that is away from and behind the conditioner disk 50 (shown by the region 204 of the path 200 and referred to as "trailing off-conditioner data"). The leading off-conditioner data and the trailing off-conditioner data can each correspond to an arc of travel of 5 to 30° along the path 200 by the sensor 102.

[0034] FIG. 3 shows an example of an acoustic signal 300. As shown, the signal intensity can increase when the sensor 102 is disposed below the conditioner disk 50, i.e., during the "on-conditioner data". The acoustic monitoring system 100 can process the acoustic signal 300 and re-segment the acoustic signal 300 into segments, which can assist in subsequent signal processing.

[0035] Generally, at least the on-conditioner data 226 is used for monitoring the conditioner disk 50 described below. In some implementations, the leading-off conditioner data 222 and / or the trailing-off conditioner data 230 are also used for monitoring the conditioner disk 50. However, in some implementations, only the on-conditioner data is used. The portions of the signals not used in conditioner disk monitoring can still be used for other monitoring purposes, such as detecting the polishing endpoint or detecting defects on the substrate 10.

[0036] Returning to FIG. 1, the acoustic signal generated by the interface between the conditioner disk 50 and the polishing layer 112 of the polishing pad 110 travels through the polishing pad 110 and is received by the acoustic sensor 102. The acoustic sensor 102 transmits what is received to the signal processing electronics 110 that performs functions on the received acoustic signal. The electronics 110 can include, for example, a filter, an amplifier, a spectrum analyzer, a data acquisition system (DAQ), or other components for processing the received acoustic signal. Generally, the electronics 110 can include a general-purpose programmable computer, a dedicated circuit, or a combination thereof. In some implementations, the electronics 110 is within the controller 90 and is implemented, for example, by the controller 90.

[0037] For example, after amplification, preliminary filtering, and digitization, the signal from the acoustic sensor 102 can undergo data processing, for example, in the controller 190, for detecting the wear state of the conditioner disk 50 and / or for detecting other anomalies of the conditioner head 46. The controller 90 can generate an alert indicating the type of event, for example, the alert can indicate that the conditioner disk needs to be replaced, or that the conditioner disk is not properly attached to the conditioner head, or that the pressure by the conditioner disk does not match what is expected.

[0038] In some implementations, the controller 90 is configured to monitor changes in the acoustic signal intensity. For example, in an active acoustic monitoring system (where the sensor 102 emits acoustic energy), the intensity of the received signal is compared to the intensity of the emitted signal to generate a normalized signal, and the normalized signal can be monitored over time to detect changes. As another example, in a passive acoustic monitoring system, the intensity of the received signal is compared to a measured initial signal intensity, for example, obtained when the conditioner disk was newly installed on the carrier head, to generate a normalized signal, and the normalized signal can be monitored over time to detect changes. Such changes indicate a change in the conditioner disk and can, for example, indicate that the conditioner disk is worn and needs to be replaced.

[0039] As another example, the amount of noise in the signal, for example, the deviation such as the rms variance of the signal, is monitored. For example, the deviation value calculated for the signal can be compared to a threshold value. If the deviation value exceeds the threshold value, this indicates a change in the conditioner disk and can, for example, indicate that the conditioner disk is worn and needs to be replaced.

[0040] In some implementations, frequency analysis of the signal is performed. For example, frequency domain analysis can be used to determine the change in relative power of the spectral frequency. In particular, a Fourier transform, such as a fast Fourier transform (FFT), can be performed on the signal to generate a spectrum (e.g., a power, wavelength, or frequency spectrum). A particular band of power, wavelength, or frequency can be monitored, and if the intensity in that band exceeds a threshold, this can indicate that the conditioner disk is worn and needs to be replaced. Alternatively, if the location (e.g., wavelength) or bandwidth of a local maximum or minimum in a selected frequency range exceeds a threshold, this can indicate a change in the conditioner disk, for example, that the conditioner disk is worn and needs to be replaced.

[0041] In some implementations, the spectrum of the signal can be compared to a reference spectrum. If the difference, such as the sum of the squares of the differences over a power, wavelength, or frequency range, exceeds or falls below a threshold, this can indicate a change in the conditioner disk, for example, that the conditioner disk is worn and needs to be replaced.

[0042] The determination of the appropriate characteristics of the signal to be monitored and the appropriate criteria for triggering an indication of a change in the conditioner disk can be made empirically. For example, polishing can be performed with a worn conditioning disk. For example, the disk is known to have a low polishing pad wear rate, and the spectrum of the signal from this conditioning disk can be used as a reference spectrum. As another example, polishing can be performed with both a new conditioning disk and a worn conditioning disk. The spectra of the signals are compared to empirically determine the power, wavelength, or frequency band for monitoring and whether the worn conditioner disk has a higher or lower signal intensity within that band. A criterion for the signal can be derived to generate an alert indicating that the conditioner disk is worn and needs to be replaced, and the controller 90 can be configured to test whether the signal meets that criterion.

[0043] As another example, polishing can be performed with a conditioning disk known to be improperly installed on the conditioner head, and the spectrum of the signal from this improperly installed conditioning disk can be used as a reference spectrum. As another example, polishing can be performed with both a properly installed conditioning disk and an improperly installed conditioning disk. The spectra of the signals are compared to empirically determine the power, wavelength, or frequency band for monitoring and whether the improperly installed conditioner disk has a higher or lower signal intensity within that band. A criterion for the signal can be derived to generate an alert indicating that the conditioner disk is not properly installed, and the controller 90 can be configured to test whether the signal meets that criterion.

[0044] As another example, the polishing can be performed with a new conditioner disk, and the spectrum of the signal from the new disk can be used as a reference spectrum. This can provide a "gold" signal spectrum. If the measured spectrum of another disk deviates from the reference spectrum, this can indicate a problem. The controller 90 can then analyze which of the other known problems, such as a worn or improperly installed conditioner disk, provides the closest fit. If the spectrum corresponding to a known problem does not match the measured spectrum within a threshold, the system can generate a general fault signal indicating an unknown problem.

[0045] As another example, the polishing can be performed with a conditioner disk under a first load corresponding to a desired pressure set by the polishing strategy, and the polishing can also be performed with a conditioner disk under a different second load, such as a lower load. At a lower load on the conditioner disk, there is lower friction and thus there should be a lower signal from the acoustic monitoring system. The spectra of the signals can be compared to empirically determine a power, wavelength, or frequency band for monitoring whether the friction on the conditioning disk (and thus the load applied to it) matches the expected value. A reference for the signal can be derived to generate an alert indicating that the load on the conditioner disk does not match the expected load, and the controller 90 can be configured to test whether the signal meets that reference.

[0046] During operation, acoustic signals are collected from the in-situ acoustic monitoring system 160. The signals are monitored to detect changes in the conditioner disk or other problems related to the conditioner head. Detection of a change or problem can trigger an alert to the operator or automatically stop the polishing operation. The conditioner disk can be removed, replaced, or removed and reinstalled depending on the nature of the problem.

[0047] Figure 4 shows another implementation of the in-situ acoustic monitoring system where the sensor 102 is attached to the conditioner head 46 rather than being supported by the platen. This simplifies signal processing in that the controller 90 does not need to select the portion of the signal corresponding to the sensor 102 passing under the conditioner disk 50. On the other hand, position information is lost and the sensor 102 may pick up acoustic signals from the entire conditioning disk 50 and does not have an off-conditioner signal for calibration.

[0048] The controller 90 and the other controls for the other functional operations described herein can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, or in combinations thereof. The controller 90 and the other functionality can be implemented using one or more non-transitory computer program products, i.e., one or more computer programs tangibly embodied in a machine-readable storage device, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple processors or computers. The controller 90 and the other functionality can be implemented using one or more programmable processors executing one or more computer programs, e.g., in a general-purpose computer, or using dedicated logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0049] Some embodiments of the present invention have been described. However, it will be understood that various modifications can be made. For example, · Instead of sweeping along an arcuate path, the conditioner head can be moved linearly, for example, conveyed along a linear rail. · The polishing pad can be a belt driven by a roller rather than a circular pad on the platen. · The polishing pad can be a fixed abrasive polishing pad or other material.

[0050] Although this specification contains many details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Also, some of the features described in this specification in the context of separate implementations can be combined. Conversely, the various features described in the context of a single implementation can be implemented separately in multiple embodiments or in any suitable sub-combination.

Claims

1. A platen for supporting a polishing pad, A conditioner head for keeping a conditioner disk in contact with the polishing pad, A motor for generating relative movement between the polishing pad and the conditioner disk so as to condition the polishing pad, An in-situ acoustic monitoring system having an acoustic sensor for receiving an acoustic signal from the conditioner disk, A controller configured to analyze an output signal from the acoustic sensor and determine characteristics of the conditioner disk or the conditioner head based on the output signal A chemical mechanical polishing apparatus comprising the same.

2. The apparatus according to claim 1, wherein the acoustic sensor is housed in the platen.

3. The apparatus according to claim 2, wherein the acoustic sensor contacts the bottom surface of the polishing pad.

4. The apparatus according to claim 2, wherein the controller is configured to identify a portion of the signal corresponding to the acoustic sensor located below the conditioner disk.

5. The apparatus according to claim 4, wherein the controller is configured to use only the portion of the signal corresponding to the acoustic sensor located below the conditioner disk to determine the characteristics of the conditioner disk or the conditioner head.

6. The apparatus according to claim 1, wherein the acoustic sensor is attached to the conditioner head.

7. The apparatus according to claim 1, wherein the controller is configured to detect an acoustic event resulting from friction of the conditioner disk against a polishing surface.

8. The apparatus according to claim 1, wherein the controller is configured to perform at least one of generating an alert, stopping the polishing, or changing conditioning parameters based on the determined characteristics of the conditioning disk or the conditioning head.

9. The apparatus according to claim 8, wherein the controller is configured to detect that the conditioning disk is worn sufficiently to require replacement.

10. The apparatus according to claim 8, wherein the controller is configured to detect that the conditioning disk is improperly installed on the conditioning head.

11. The apparatus according to claim 8, wherein the controller is configured to detect that the pressure of the conditioning disk on the polishing pad does not match a desired pressure.

12. The apparatus according to claim 1, wherein the controller is configured to generate a measured spectrum of the output signal.

13. The apparatus according to claim 12, wherein the controller is configured to compare the measured spectrum with a reference spectrum.

14. The apparatus according to claim 12, wherein the controller is configured to detect a signal intensity in a band in the measured spectrum and compare the signal intensity with a threshold.

15. A method of monitoring a conditioning disk, comprising: receiving, by an acoustic sensor, an acoustic signal from the conditioning disk while the conditioning disk conditions a polishing pad, and generating an output signal from the acoustic sensor; analyzing the output signal and determining a characteristic of the conditioning disk or a conditioning head based on the output signal; A method comprising **Claim 16** The method according to claim 15, comprising sweeping the acoustic sensor below the conditioning disk and determining a portion of the output signal corresponding to the acoustic sensor below the conditioning disk. **Claim 17** The method according to claim 16, comprising using only the portion of the output signal corresponding to the acoustic sensor when determining the characteristics of the conditioning disk or the conditioning head. **Claim 18** The method according to claim 15, comprising detecting that the conditioning disk is worn sufficiently to require replacement. **Claim 19** The method according to claim 15, comprising detecting that the conditioning disk is improperly installed on the conditioning head. **Claim 20** The method according to claim 15, comprising detecting that the pressure of the conditioning disk on the polishing pad does not match a desired pressure.

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