Acoustic monitoring of conditioner during polishing

Abstract

A chemical mechanical polishing device comprises a platen for supporting a polishing pad, a conditioner head for holding a conditioner disc in contact with the polishing pad, a motor for generating relative movement between the polishing pad and the conditioner disc to condition the polishing pad, an on-site acoustic monitoring system having an acoustic sensor for receiving acoustic signals from the conditioner disc, and a controller configured to analyze signals from the acoustic sensor and determine characteristics of the conditioner disc or conditioner head based on the signals.

Description

Technology Field

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

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconducting, or insulating layers onto a silicon wafer. One manufacturing step involves depositing a filler layer on a non-planar surface and planarizing the filler layer. In certain applications, the filler layer is planarized until the top surface of the patterned layer is exposed. For example, a conductive filler layer may be deposited on a patterned insulating layer to fill trenches or holes within the insulating layer. After planarization, 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 filler 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 planarization method. This planarization method typically requires a substrate to be mounted on a carrier or polishing head. The exposed surface of the substrate is typically positioned 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 typically supplied to the surface of the polishing pad.

[0004] When the grinder is in operation, the pad undergoes compression, shear, and friction that cause heat and wear. Abrasive material from the slurry, wafer, and pad is pressurized into the pores of the pad material, and the material itself becomes matt and even partially fused. These effects, sometimes referred to as "glazing," reduce the roughness of the pad and its ability to apply fresh slurry to the substrate. Therefore, it is desirable to condition the pad by removing the trapped slurry and preventing the pad material from matting, or by re-expanding or re-roughening it.

[0005] A polishing system typically includes a conditioner system for conditioning a polishing pad. Conditioning the polishing pad maintains the polishing surface at a consistent roughness to ensure uniform polishing conditions for each wafer. Conventional conditioner systems have a conditioner head that holds a conditioner disc having abrasive under-surfaces, which are positioned to contact the polishing pad and, for example, have diamond particles. Contact and movement of the abrasive surfaces with respect to the polishing pad roughens the polishing surface. However, the conditioner disc itself undergoes wear and needs to be replaced periodically.

[0006] In one embodiment, the chemical mechanical polishing device comprises a platen for supporting a polishing pad, a conditioner head for holding a conditioner disc in contact with the polishing pad, a motor for generating relative movement between the polishing pad and the conditioner disc to condition the polishing pad, an on-site acoustic monitoring system having an acoustic sensor for receiving acoustic signals from the conditioner disc, and a controller configured to analyze signals from the acoustic sensor and determine characteristics of the conditioner disc or conditioner head based on the signals.

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

[0008] Wear on the conditioning disc can be monitored in the field, and the end-of-life of the conditioner disc can be detected more reliably in the field. When the end-of-life of the conditioner is detected, a warning can be generated to trigger the replacement of the conditioner disc. The risk of defects or scratches on the substrate can be reduced. The effective life of the conditioner discs can be improved, and downtime for conditioner disc replacement can be reduced, thereby improving the cost of ownership. Other abnormal conditions associated with the conditioner can be detected, and a warning can be generated to trigger corrective action. For example, improper installation of the conditioner disc or incorrect conditioning downforce can be detected.

[0009] Details of one or more embodiments are listed in the accompanying drawings and the description below. Other features and advantages are apparent from the description, drawings, and claims. Brief explanation of the drawing

[0010] Figure 1 is a schematic side view of a polishing system including a conditioner and an on-site acoustic monitoring system. Figure 2a is a schematic plan view of a grinding system. Figure 2b is a diagram of signal splitting from an acoustic sensor based on the relative position of the conditioner. FIG. 3 is a drawing of exemplary acoustic signals and segments corresponding to different parts of a ring assembly or substrate. FIG. 4 is a schematic side view of a polishing system including a conditioner and another implementation of a field acoustic monitoring system. In the drawings, the same reference numbers indicate the same elements. Specific details for implementing the invention

[0011] The chemical mechanical polishing process may include a pad conditioning step in which a conditioner disc, such as a disc coated with abrasive diamond particles, is pressed against a rotating polishing pad to condition and texture the surface of the polishing pad. However, friction of the pad against the abrasive particles of the conditioner disc and / or chemicals in the polishing fluid can cause the conditioner disc to wear down gradually. For example, the abrasive particles may become dull, reducing the wear rate, or may detach from the conditioner disc, resulting in scratches and defects on the substrate. Consequently, the conditioning disc needs to be replaced periodically. However, due to simple manufacturing variations, the conditioning discs may not all have the same lifespan.

[0012] One approach is simply to replace the conditioning disc after a set interval, for example, after polishing a preset number of substrates or after a preset usage time. However, this entails the risk of both underuse of the conditioning disc—that is, replacing a disc that still has a valid life—and overuse, which carries the risk of damage to the substrate. Another approach is to monitor the wear of the polishing pad; changes in the wear rate can indicate a problem with the conditioner disc. However, this is an indirect indication; the conditioner disc may experience wear and the risk of separation of abrasive particles without a change in the wear rate.

[0013] Monitoring acoustic signals from the conditioner disc can resolve these issues and may be a more reliable technique for detecting when the conditioner disc needs to be replaced. Even without monitoring the conditioner disc's lifespan, acoustic monitoring can provide indications of other abnormal conditions, allowing the grinding system operator to take corrective action.

[0014] As illustrated in FIGS. 1 and 2a, the chemical mechanical polishing system (20) includes a rotatable platen (24) on which a polishing pad (30) is placed. 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) may be a two-layer polishing pad having an outer polishing layer (34) having a polishing surface (36) and a softer back layer (32).

[0015] The polishing system (20) includes a supply port (64) at the end of, for example, a slurry supply arm (62) to distribute a polishing liquid (60), such as an abrasive slurry, onto a polishing pad (30). In some embodiments, the polishing system (20) includes a wiper blade or body for uniformly distributing the polishing liquid (60) over the polishing pad (30).

[0016] The carrier head (70) is suspended from a support structure (72), such as a carousel or track, and is connected to a carrier head rotation motor (76) by a drive shaft (74), thereby allowing the carrier head to rotate about an axis (71) (see arrow B in FIG. 2a). Optionally, the carrier head (70) may vibrate laterally (see arrow C in FIG. 2a) on sliders, such as those on the carousel or track (72); or vibrate by rotational vibration of the carousel itself. In operation, the platen rotates about its central axis (25), and the carrier head rotates about its central axis (71) and also translates laterally across the uppermost surface of the polishing pad (30). The carrier head (70) may include a flexible membrane (80) having a substrate mounting surface for contacting the rear surface of the substrate (10), and a plurality of pressurizable chambers (82) for applying different pressures to different zones on the substrate (10), e.g., different radial zones. For convenience of illustration, three chambers are shown in FIG. 1, but one or two chambers, or four or more chambers, e.g., five chambers may exist. The carrier head (70) may also include a retaining ring (84) for holding the substrate under the membrane (80).

[0017] A controller (90), such as a programmable computer, is connected to motors (121), (154) to control the rotational speed of the platen (120) and the carrier head (140). For example, each motor may include an encoder that measures the rotational speed of the associated drive shaft.

[0018] The polishing station (20) also includes a pad conditioner (40) having a conditioner disk (50) to maintain the surface roughness (30) of the polishing pad. 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 may be provided by abrasive diamond particles (54) fixed to the lower surface of a back plate. The back plate (54) is typically a metal such as stainless steel, but other materials such as ceramic are possible. In some embodiments, abrasive particles of other compositions, for example, silicon carbide, are used instead of or in addition to diamond particles.

[0019] During conditioning, the abrasive areas move relative to the surface (30) of the polishing pad to polish and retexture 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).

[0020] The conditioner disc (50) can be held by the conditioner head (46) at the end of the arm (42). The arm (42) and the conditioner head (46) are supported by the base (48). The arm (42) can swing to sweep the conditioner head (46) and the conditioner disc (50) laterally across the polishing pad (30) (see arrow E in FIG. 2a). For example, the base (48) can be driven by a motor (49) to pivot about a vertical axis, thereby sweeping the arm (42) and the conditioner head (46) laterally over the platen (24) and the polishing pad (30).

[0021] The conditioner head (46) includes mechanisms for attaching the conditioner disc (50) to the conditioner head (46) (e.g., mechanical attachment systems, e.g., bolts or screws, or magnetic attachment systems), and mechanisms for rotating the conditioner disc (50) about an axis (41) (e.g., drive belts through arms or rotors inside the conditioner head). Additionally, the pad conditioner (40) may also include mechanisms for adjusting the pressure between the conditioner disc (50) and the polishing pad (30) and / or changing the vertical position of the conditioner disc (50) relative to the polishing pad (30) (e.g., pneumatic or mechanical actuators inside the conditioning head or base). For example, the conditioner head (46) may include an upper portion (46a), a lower portion (46b) holding the conditioner disc (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 disc (50) on the polishing pad (30). However, these mechanisms may have many possible implementations (and are not limited to those shown in FIG. 1). As other examples, a vertical actuator may be positioned on the base (48) to lift and lower the arm (42), or the arm may be pivotably attached to the base (48) in such a way that it allows the conditioner head (46) to swing vertically to lift and lower the conditioner head (46) from the polishing pad (30).

[0022] The polishing system (20) includes at least one field acoustic monitoring system (100). The field acoustic monitoring system (100) includes an acoustic sensor (102). In the embodiment illustrated in FIG. 1, the acoustic sensor (102) is located on the substrate (10) side further away from the polishing pad (30) and will receive acoustic signals from the substrate conditioner disk (50) through the polishing pad (30). In particular, the acoustic sensor (102) may be supported on a platen (24). For example, the acoustic sensor (102) may be located in a recess (28) within the platen (24). In some embodiments, the top surface of the acoustic sensor (102) is coplanar with the top surface of the platen (24).

[0023] The acoustic sensor (102) is positioned radially (from the axis (25)) on the platen (24) so ​​that the sensor (102) sweeps under the conditioner disk (50) for at least some lateral positions of the conditioner head (46). For example, the acoustic sensor (102) may be positioned at an intermediate point between the edge of the platen (24) and the axis of rotation (25).

[0024] In some implementations, the portion of the polishing pad immediately above the acoustic sensor (102) may include an acoustic window (120), for example, an area having an acoustic impedance lower than that of the surrounding polishing material. The acoustic window (120) may extend through the polishing layer (32), the back layer (34), or both. However, if the acoustic transmission of the polishing pad is sufficiently high, the acoustic window (120) may not be necessary.

[0025] The acoustic sensor (102) may be a contact acoustic sensor having a surface connected to a part of the polishing pad, such as the polishing layer (32), the back layer (34), or the acoustic window (120) (e.g., having only an adhesive layer for direct contact therewith or for attachment thereto, or having only an acoustic gel for transmitting an acoustic signal therefrom). For example, the acoustic sensor (102) may be an electromagnetic acoustic transducer or a piezoelectric acoustic transducer. The piezoelectric sensor may include a rigid contact plate, such as stainless steel, positioned to contact the body to be monitored, and a piezoelectric assembly on the back of the contact plate, such as a piezoelectric layer interposed between two electrodes.

[0026] In some implementations, the spring (106) is positioned to press 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.

[0027] The acoustic sensor (102) may be connected to a power source and / or other signal processing electronics (110) via a rotary coupling (112), such as a mercury slip ring, by a circuit (108). The signal processing electronics (110) may eventually be connected to a controller (90). In some implementations, some or all of the functionality of the signal processing electronics (110) is performed by the controller (90).

[0028] In some implementations, the field acoustic monitoring system (100) is a passive acoustic monitoring system. In this case, signals are monitored by an acoustic sensor (102) without generating signals from an acoustic signal generator (or the acoustic signal generator may be completely omitted from the system). The passive acoustic signals monitored by the acoustic sensor (162) may be in the range of 50 kHz to 1 MHz, for example, 200 to 400 kHz, or 200 kHz to 1 MHz.

[0029] The signal from the sensor (102) can be amplified by a built-in internal amplifier. In some implementations, the amplification gain is 40 to 60 dB (e.g., 50 dB). Next, the signal from the acoustic sensor (106) can be further amplified and filtered as needed and digitized, for example, via an A / D port to a high-speed data acquisition board within an electronic device (108 or 110). Data from the acoustic sensor (102) can be recorded in a range of 1 to 10 MHz, for example, 1-3 MHz or 6-8 MHz. In implementations where the acoustic sensor (162) is a passive acoustic sensor, a frequency range of 100 kHz to 2 MHz, for example, 500 kHz to 1 MHz (e.g., 750 kHz), can be monitored.

[0030] An optical interrupter connected to a position sensor, for example, the edge of the platen or a rotary encoder, can be used to detect the angular position of the platen (24). This allows only parts of the signal measured when the sensor (102) is close to the conditioner disk (50), for example, when the sensor (102) is under the conditioner disk (50), to be used in subsequent signal processing to indicate the conditioner disk condition.

[0031] Referring to FIG. 2a, due to the movement of the platen (24) (indicated by arrow A), the acoustic sensor (102) sweeps along a path (200) moving under the conditioner disk (50). An acoustic monitoring system (100), such as a controller (90), may be configured to sample signals from the sensor (102) when the sensor is passing under the conditioner disk (50). For example, the controller (90) may determine the angular position of the sensor (102) based on input from a motor encoder or a platen position sensor and compare this with the position of the conditioner head, for example, based on conditioner sweep information. Determination of the position of the sensor relative to the substrate is discussed in U.S. Patent No. 6,159,073 and U.S. Patent No. 6,296,548, and equivalent techniques may be applied to the moving conditioner disk. This allows parts of the signal received when the sensor (102) is under the conditioner disk (50) to be identified and selected.

[0032] Referring to FIGS. 2a and 2b, a signal (220) from a sensor (102) may include a portion (222) corresponding to the sensor (102) being off but approaching the conditioner disk (50) (indicated by the area (202) of the path (200) and referred to as "leading off-conditioner data"), a portion (224) corresponding to the sensor (102) being below the conditioner disk (50) (referred to as "on-conditioner data"), and a portion (222) corresponding to the sensor (102) being off and after the conditioner disk (50) (indicated by the area (204) of the path (200) and referred to as "trailing off-conditioner data"). The preceding and succeeding off-conditioner data can each correspond to an arc of movement of 5-30° along the path (200) by the sensor (102).

[0033] FIG. 3 illustrates an example of an acoustic signal (300). As illustrated, when the sensor (102) is positioned under the conditioner disk (50), that is, in the case of "on-conditioner data," the signal strength may increase. The acoustic monitoring system (100) can process the acoustic signal (300) and subdivide the acoustic signal (300) into segments, which can assist in subsequent signal processing.

[0034] Generally, at least on-conditioner data (226) is used for monitoring the conditioner disk (50) discussed below. In some implementations, preceding off-conditioner data (222) and / or trailing off-conditioner data (230) are also used for monitoring the conditioner disk (50). However, in some implementations, only on-conditioner data is used. Parts of the signal not used for conditioner disk monitoring may still be used for other monitoring purposes, such as detecting polishing endpoints or detecting defects on the substrate (10).

[0035] Returning to FIG. 1, acoustic signals generated by the interface between the conditioner disk (50) and the polishing layer (112) of the polishing pad (110) travel through the polishing pad (110) and are received by an acoustic sensor (102). The acoustic sensor (102) transmits the received signals to signal processing electronics (110) that perform functions for the received acoustic signals. The electronics (110) may include, for example, a filter, an amplifier, a spectrum analyzer, a data acquisition system (DAQ), or other components for processing the received acoustic signals. Generally, the electronics (110) may include a general-purpose programmable computer, a dedicated circuit, or a combination thereof. In some implementations, the electronics (110) are located within a controller (90), for example, implemented by the controller.

[0036] For example, the signal from the acoustic sensor (102) after amplification, preliminary filtering, and digitization may undergo data processing in, for example, a controller (190) for detecting the wear condition of the conditioner disk (50) and / or other abnormal conditions of the conditioner head (46). The controller (90) may generate a warning indicating the type of event, for example, that the warning may indicate that the conditioner disk needs to be replaced, that the conditioner disk is not properly attached to the conditioner head, or that the pressure exerted by the conditioner disk does not match what is expected.

[0037] In some implementations, the controller (90) is configured to monitor changes in acoustic signal strength. For example, in the case of an active acoustic monitoring system (where the sensor (102) emits acoustic energy), the received signal strength is compared with the emitted signal strength to generate a normalized signal, and the normalized signal can be monitored over time to detect changes. As another example, in the case of a passive acoustic monitoring system, the received signal strength is compared with the measured initial signal strength acquired, for example, when the conditioner disk is 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 can indicate changes in the conditioner disk, for example, that the conditioner disk is worn out and needs to be replaced.

[0038] As another example, deviations such as the amount of noise in the signal, e.g., the signal's RMS variance, are monitored. For example, a deviation value calculated for the signal can be compared to a threshold value. If the deviation value exceeds the threshold value, this may indicate a change in the conditioner disk, such as that the conditioner disk is worn out and needs to be replaced.

[0039] In some implementations, frequency analysis of the signal is performed. For example, frequency domain analysis may be used to determine changes in power relative to spectral frequencies. In particular, a Fourier transform, such as a Fast Fourier Transform (FFT), may be performed on the signal to generate a spectrum (e.g., power, wavelength, or frequency spectrum). Specific bands of power, wavelength, or frequency may be monitored, and if the intensity in a band exceeds a threshold, this may indicate that the conditioner disk is worn out and needs to be replaced. Alternatively, if the location of a maximum or minimum value (e.g., wavelength) or bandwidth within a selected frequency range exceeds a threshold, this may indicate a change in the conditioner disk, such as that the conditioner disk is worn out and needs to be replaced.

[0040] In some implementations, the spectrum of the signal can be compared to a reference spectrum. If the sum of the squared differences, e.g., power, wavelength, or across a frequency range, exceeds a threshold or falls below it, this may indicate a change in the conditioner disk, e.g., that the conditioner disk is worn out and needs to be replaced.

[0041] The appropriate characteristics of the signal to be monitored and the appropriate criteria for triggering the indication of changes in the conditioner disc can be determined empirically. For example, polishing can be performed with a worn conditioning disc, for instance, which is known to have a low polishing pad wear rate, and the spectrum of the signal from such a conditioning disc can be used as a reference spectrum. As another example, polishing can be performed with both a fresh conditioning disc and a worn conditioning disc. The spectra of the signals can be compared to empirically determine the power, wavelength, or frequency band for monitoring, and whether the worn conditioner disc has a higher or lower signal intensity within that band. Criteria for generating a warning indicating that the signal is worn and needs to be replaced can be derived, and the controller (90) can be configured to test whether the signal meets the criteria.

[0042] As another example, polishing may be performed with a conditioner disc known to be improperly installed on a conditioner head, and the spectrum of the signal from this improperly installed conditioner disc may be used as a reference spectrum. As another example, polishing may be performed with both a properly installed conditioner disc and an improperly installed conditioner disc. The spectra of the signals may be compared to determine, empirically, whether the power, wavelength, or frequency band for monitoring, and whether the improperly installed conditioner disc has a higher or lower signal intensity within that band. A criterion for generating a warning that the signal indicates the conditioner disc is not properly installed may be derived, and the controller (90) may be configured to test whether the signal meets the criterion.

[0043] As another example, polishing can be performed with a fresh conditioner disc, and the spectrum of the signal from the fresh disc can be used as a reference spectrum. This can provide a "gold" signal spectrum. If the measured spectrum of another disc deviates from the reference spectrum, this may indicate a problem. Then, the controller (90) can analyze which of the other known problems, such as a worn or improperly installed conditioner disc, provides the closest fit. If the spectra corresponding to the known problems fail to fit the measured spectrum within a threshold, the system may generate a general fault signal indicating an unknown problem.

[0044] As another example, grinding can be performed on a conditioner disc under a first load corresponding to a desired pressure set by a grinding recipe, and grinding can be performed on a conditioner disc under a different second load, e.g., a lower load. Under a lower load on the conditioner disc, there is lower friction and therefore a lower signal from the acoustic monitoring system. Spectra of the signals can be compared to empirically determine a power, wavelength, or frequency band to monitor whether the friction on the conditioning disc (and thus the load applied thereto) matches the expected value. A criterion can be derived for generating a warning that the signal does not match the expected load, and the controller (90) can be configured to test whether the signal meets the criterion.

[0045] During operation, an acoustic signal is collected from the field acoustic monitoring system (160). The signal is monitored to detect changes in the conditioner disc or other problems related to the conditioner head. Detection of changes or problems may trigger a warning to the operator or automatically stop the polishing operation. The conditioner disc may be removed and replaced or removed and reinstalled, depending on the nature of the problem.

[0046] FIG. 4 illustrates another implementation of a field acoustic monitoring system in which the sensor (102) is attached to the conditioner head (46) rather than being supported by a platen. This simplifies signal processing in that the controller (90) does not need to select parts of the signal corresponding to the sensor (102) passing under the conditioner disk (50). On the other hand, position information is lost; the sensor (102) is likely to pick up acoustic signals from the entire conditioning disk (50) and does not have an off-conditioner signal to correct for.

[0047] The controller (90) and other control of other functional operations described herein may be implemented as a digital electronic circuit, or as computer software, firmware, or hardware, or a combination thereof. The controller (90) and other functions may be implemented using one or more non-transient computer program products, namely, one or more computer programs tangibly implemented in a machine-readable storage device for execution by a data processing device, such as a programmable processor, a computer, or a plurality of processors or computers, or for controlling its operation. The controller (90) and other functions may be implemented using one or more programmable processors that execute one or more computer programs in a general-purpose computer, for example, or using special-purpose logic circuits, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

[0048] Many embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made. For example:

[0049] ● Instead of sweeping along an arched path, the conditioner head can be moved linearly, for example, transported along a linear rail.

[0050] ● The grinding pad may be a belt driven by rollers, rather than a circular pad on a platen.

[0051] ● The abrasive pad may be a fixed abrasive pad or other material.

[0052] Although this specification contains many details, they should not be interpreted as limitations on the scope of what may be claimed, but rather as descriptions of features specific to specific examples. Specific features described in this specification may also be combined in the context of distinct implementations. Conversely, various features described in the context of a single implementation may also be implemented separately or in any suitable sub-combination in multiple embodiments.

Claims

Claim 1 A chemical mechanical polishing device comprising: a platen for supporting a polishing pad; a conditioner head for holding a conditioner disc in contact with the polishing pad; a motor for generating relative movement between the polishing pad and the conditioner disc to condition the polishing pad; an on-site acoustic monitoring system having an acoustic sensor for receiving acoustic signals from the conditioner disc—the acoustic sensor is attached to the conditioner head—; and a controller configured to analyze an output signal from the acoustic sensor and determine the state of the conditioner disc or the conditioner head based on the output signal—the controller is configured to generate a measured spectrum of the output signal and compare the measured spectrum with a reference spectrum. Claim 2 A device according to claim 1, wherein the controller is configured to detect acoustic events caused by friction of the conditioner disk against the polishing surface of the polishing pad. Claim 3 A device according to claim 1, wherein the controller is configured to perform at least one of generating a warning, stopping polishing, or changing conditioning parameters based on a determined state of the conditioner disk or the conditioner head. Claim 4 In claim 3, the device is configured such that the controller detects that the conditioner disk is sufficiently worn to require replacement. Claim 5 In claim 3, the device is configured such that the controller detects that the conditioner disk is improperly installed on the conditioner head. Claim 6 In claim 3, the device is configured such that the controller detects that the pressure of the conditioner disk on the polishing pad does not match the desired pressure. Claim 7 A method for monitoring a conditioner disc, comprising the steps of: receiving acoustic signals from an acoustic sensor from the conditioner disc while the conditioner disc is conditioning a polishing pad, wherein the acoustic sensor is attached to a conditioner head that holds the conditioner disc; generating an output signal from the acoustic sensor; analyzing the output signal and determining the state of the conditioner disc or the conditioner head based on the output signal, including generating a measured spectrum of the output signal and comparing the measured spectrum with a reference spectrum. Claim 8 A method according to claim 7, comprising the step of detecting that the conditioner disc is sufficiently worn to require replacement. Claim 9 A method according to claim 7, comprising the step of detecting that the conditioner disk is improperly installed on the conditioner head. Claim 10 A method according to claim 7, comprising the step of detecting that the pressure of the conditioner disc on the polishing pad does not match the desired pressure.

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