Acoustic monitoring for ensuring process reliability during polishing

Abstract

Disclosed herein is a chemical mechanical polishing apparatus including a platform to support a polishing pad; a carrier head for holding the surface of the substrate against the polishing pad; the motor is used for generating relative motion between the platform and the carrying head so as to polish the overlying layer on the substrate; an in-situ acoustic monitoring system including an acoustic sensor that receives acoustic energy from the substrate and the polishing pad; and a controller configured to detect an anomalous acoustic event based on measurements from the in-situ acoustic monitoring system and determine a type of anomaly based on signals measured by the in-situ acoustic monitoring system during the anomalous acoustic event.

Description

Technical Field

[0001] This disclosure relates to chemical mechanical polishing, and more specifically to the detection of abnormal events in acoustic signals received during chemical mechanical polishing. Background Technology

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconducting, or insulating layers on a silicon wafer. One fabrication step involves depositing a filler layer on a non-planar surface and planarizing the filler layer. For some applications, the filler layer is planarized until the top surface of the underlying patterned layer is exposed. For example, a conductive filler layer may be deposited on a patterned insulating layer to fill trenches or holes in 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. For other applications (such as oxide polishing), the filler layer is planarized until a predetermined thickness is left on the non-planar surface. Additionally, photolithography processes often require the planarization of the substrate surface.

[0003] Chemical mechanical polishing (CMP) is a widely accepted planarization method. This method typically requires mounting a substrate on a carrier or polishing head. The exposed surface of the substrate is usually placed against a rotating polishing pad. The carrier head provides a controlled load on the substrate to push it against the polishing pad. An abrasive polishing slurry is typically supplied to the surface of the polishing pad.

[0004] Acoustic monitoring has been proposed for monitoring the progress of polishing processes, and more specifically for detecting the exposure of underlying layers, such as patterned barrier layers or dielectric layers, during metal polishing. Summary of the Invention

[0005] In one aspect, a chemical mechanical polishing apparatus includes a support head for holding a substrate against a polishing pad. An in-situ acoustic monitoring system receives acoustic signals from the substrate and the support head and generates signals that are transmitted to a controller. The controller receives the signals and generates and uses signal processing to detect discrete anomalies in the time-series acoustic emission signals. The controller is configured to change one or more polishing parameters or generate a warning based on the detected anomalies.

[0006] Generally, the aspects disclosed herein are a chemical mechanical polishing apparatus comprising a platform for supporting a polishing pad; a support head for holding a substrate surface against the polishing pad; a motor for generating relative motion between the platform and the support head to polish an overlay on the substrate; an in-situ acoustic monitoring system including acoustic sensors receiving acoustic energy from the substrate and the polishing pad; and a controller configured to detect abnormal acoustic events based on measurements from the in-situ acoustic monitoring system, and to determine the type of abnormality based on signals measured by the in-situ acoustic monitoring system during the abnormal acoustic event.

[0007] Examples may include one or more of the following features. The controller may detect anomalous acoustic events based on a comparison of a signal with a previously measured value of an acoustic signal generated by friction between the test substrate and the polishing pad. Detection of anomalous acoustic events may be based on the controller determining the power spectrum of the acoustic signal; determining the difference between the power spectrum and a reference power spectrum stored in a storage component of the device; and detecting the anomalous acoustic event based on the difference. The controller may be configured to store a catalog that may include multiple anomaly types and at least one criterion for each anomaly type. The at least one criterion includes similarity to a reference spectrum representing the anomaly type. The controller may be configured to store different reference spectra for each different anomaly type. Anomaly types include at least one of scratches on the substrate surface, unexpected film type, poor pad flushing transition, or air bubbles between the substrate and the polishing pad. The anomaly type may include an unexpected film type, and the determination may be based on comparing the acoustic signal with a previously measured value of an acoustic signal generated by the test substrate (which may include the expected film type) and the polishing pad. The anomaly type may include a poor pad flushing transition. The anomaly type may include air bubbles between the substrate and the polishing pad. Acoustic sensors can be placed in recesses on the top surface of the platform.

[0008] Generally, the aspects disclosed herein are a chemical mechanical polishing apparatus comprising: a platform for supporting a polishing pad; a support head for holding a substrate surface against the polishing pad; a motor for generating relative motion between the platform and the support head to polish an overlay on the substrate; a polishing liquid source for delivering the polishing liquid to the polishing pad; a rinsing liquid source for delivering rinsing liquid to the polishing pad; an in-situ acoustic monitoring system including acoustic sensors receiving acoustic energy from the substrate and the polishing pad; and a controller configured to detect defective pad rinsing transitions based on measurements from the in-situ acoustic monitoring system.

[0009] Generally, the aspects disclosed herein are chemical mechanical polishing apparatus comprising: a platform for supporting a polishing pad; a support head for holding a substrate surface against the polishing pad; a motor for generating relative motion between the platform and the support head to polish an overlay on the substrate; a polishing liquid source for delivering the polishing liquid to the polishing pad; an in-situ acoustic monitoring system including acoustic sensors receiving acoustic energy from the substrate and the polishing pad; and a controller configured to detect air bubbles in the polishing liquid between the substrate and the polishing pad.

[0010] Generally, the aspects disclosed herein are a polishing method comprising: contacting a surface of a substrate with a polishing surface of a polishing pad; generating relative motion between the substrate and the polishing pad; providing a liquid slurry to the polishing surface of the polishing pad; monitoring acoustic energy from the substrate and the polishing pad using an in-situ acoustic monitoring system including acoustic sensors; determining the presence of an anomalous acoustic event based on signals from the acoustic sensors; and identifying the type of anomalous event based on acoustic signals from the in-situ acoustic monitoring system during the anomalous acoustic event.

[0011] Examples may include one or more of the following features. The method may include generating a warning based on the determination of the presence of an anomalous acoustic event. The method may include removing a substrate surface from contact with a polishing surface based on the determination of the presence of an anomalous acoustic event or the identified type of anomalous event. The method may include identifying the type of anomalous event as a poor pad flushing transition. The method may include identifying the type of anomalous event as an inappropriate film stacking. The method may include identifying the type of anomalous event as an air bubble between the substrate and the polishing pad. The method may include removing a substrate surface from contact with a polishing surface based on the type of anomalous event.

[0012] Real-time passive monitoring of acoustic signals facilitates the detection of anomalies in acoustic emission signals, which can reduce production losses caused by inferior substrates with scratches due to excessive pad flushing. Detection of these events enables real-time process control to manage individual wafer polishing.

[0013] Real-time monitoring of changes in acoustic signals when the underlying layer is exposed can help distinguish between anticipated and unexpected events, thereby improving production efficiency and reducing losses.

[0014] Details of one or more embodiments are set forth in the accompanying drawings and the following description. Other aspects, features, and advantages will become apparent from the description and drawings and the claims. Attached Figure Description

[0015] Figure 1 This is a schematic side view of a polishing system that includes an in-situ acoustic monitoring system.

[0016] Figure 2 A schematic top view of a substrate being polished on a polishing pad, showing an instance path followed by an acoustic sensor during the polishing operation and an instance acoustic signal generated as the sensor moves along the instance path.

[0017] Figure 3 The icons represent the example acoustic signals and the segments corresponding to the signals received from below the substrate.

[0018] Figure 4 This illustration shows the transition of poorly flushed pads during planarization of the substrate surface.

[0019] Figure 5 This is a flowchart of a polishing method that includes detecting abnormal events using self-acoustic signals.

[0020] In each diagram, the same component symbol indicates the same component. Detailed Implementation

[0021] One problem with CMP is that adverse process events, such as scratches, incorrect film stacking, or poor pad flushing transitions, are not detected in real time. In some cases, adverse events are not detected until the first batch of wafers completes the process and a yield loss is observed. This can lead to significant time and cost losses. By passively monitoring acoustic signals in real time, it may be possible to detect discrete anomalies in time-series acoustic emission signals that could indicate substrate scratches or poor pad flushing transitions. Detection of these events enables real-time process control to manage individual wafer polishing. It should be noted that these discrete anomalies (e.g., in the spectrum, frequency, or both) are different from the acoustic energy generated by friction between the polishing pad and the substrate, and different from the changes in acoustic signals when the underlying layer is exposed. Furthermore, changes in acoustic signals when the underlying layer is exposed are expected and therefore not anomalous.

[0022] Another issue is the lack of real-time or tool-based means to detect these defects during wafer polishing. Furthermore, existing solutions relying on optical measurements of the wafer surface are expensive and require costly upgrades to existing systems. In contrast to optical-based solutions, passive acoustic monitoring systems reduce the costs associated with real-time monitoring and decrease the complexity and maintenance requirements of existing systems.

[0023] Figure 1 An example of a polishing apparatus 100 is illustrated. The polishing apparatus 100 includes a rotatable disc-shaped platform 120 on which a polishing pad 110 is located. The polishing pad 110 may be a two-layer polishing pad having an outer polishing layer 112 and a softer backing layer 114. The platform is operable to rotate about an axis 125. For example, a motor 121 (e.g., a DC induction motor) can rotate a drive shaft 124 to rotate the platform 120.

[0024] The polishing apparatus 100 may include a port 130 for dispensing a polishing liquid 132, such as an abrasive slurry, onto the polishing pad 110. The polishing apparatus may also include a polishing pad conditioner to abrade the polishing pad 110 in order to maintain the polishing pad 110 in a consistent abrasive state.

[0025] Polishing apparatus 100 may include a flushing arm 134 to apply a flushing liquid 136, such as water, to the polishing pad 110. The flushing liquid 136 is applied between polishing events to remove polishing liquid 132 from the polishing layer 112. In some instances, the flushing liquid 136 is applied under high pressure and / or temperature-controlled (e.g., heated or cooled) before being applied to the polishing layer 112.

[0026] The polishing apparatus 100 includes at least one carrier head 140. The carrier head 140 is operable to hold the substrate 10 against the polishing pad 110. Each carrier head 140 may have independent control over polishing parameters (e.g., pressure) associated with each respective substrate.

[0027] The carrier head 140 may include a retaining ring 142 to secure the substrate 10 beneath the flexible membrane 144. The carrier head 140 also includes one or more independently controllable pressurizable chambers (e.g., three chambers 146a-146c) defined by the membrane, which can apply independently controllable pressure to associated areas on the flexible membrane 144, and thus to the substrate 10. Although in Figure 1 The text only describes three chambers, but there may be one or two chambers, or four or more chambers, such as five chambers.

[0028] The support head 140 is suspended from a self-supporting structure 150 (e.g., a turntable or track) and connected to a support head rotation motor 154 (e.g., a DC induction motor) via a drive shaft 152, allowing the support head to rotate about axis 155. Depending on the situation, each support head 140 may oscillate laterally (e.g., on a slider on structure 150), or through rotational oscillation of the turntable itself, or by sliding along the track. In typical operation, the platform rotates about its central axis 125, and each support head rotates about its central axis 155 and translates laterally across the top surface of the polishing pad.

[0029] A controller 190, such as a programmable computer, is connected to motors 121 and 154 to control the rotational speed of platform 120 and bearing head 140. For example, each motor may include an encoder that measures the rotational speed of the associated drive shaft. A feedback control circuit (which may be in the motor itself, part of the controller, or a separate circuit) receives the measured rotational speed from the encoder and adjusts the current supplied to the motor to ensure that the rotational speed of the drive shaft matches the rotational speed received from the controller.

[0030] A position sensor (such as an optical interruptor or rotary encoder attached to the platform rim) can be used to sense the angular position of the platform 120. This allows the acoustic signal to be measured, or a portion thereof, to be recorded when the sensor 162 is near the substrate (e.g., when the sensor 162 is under the carrier head or substrate).

[0031] The polishing apparatus 100 includes at least one in-situ acoustic monitoring system 160. Specifically, the in-situ acoustic monitoring system 160 can be configured to detect acoustic emissions from the substrate 10. The in-situ acoustic monitoring system 160 includes one or more acoustic sensors 162, each generating a signal, such as a digital or analog signal, representing the acoustic waveform received at the sensor. In the presence of multiple acoustic sensors, the acoustic sensors can be mounted at different locations on the upper platform 120, for example, at equal angular intervals about the axis of rotation of the platform 120.

[0032] If positioned within platform 120, acoustic sensor 162 may be located at the center of platform 120, for example, at the axis of rotation 125, at the edge of platform 120, or at the midpoint (e.g., 5 inches from the axis of rotation for a platform with a diameter of 20 inches).

[0033] exist Figure 1 In the illustrated embodiment, the acoustic sensor 162 is positioned in a recess 164 within the platform 120 and is positioned to receive acoustic energy from the side of the substrate closer to the polishing pad 110. For example... Figure 1 As shown, the acoustic sensor 162 may extend through the aperture 138 in the backing layer 114 of the polishing pad 110 to directly contact the lower surface of the polishing layer 112. In some embodiments, the acoustic sensor 162 is (e.g.) spring-biased against the polishing layer 112. Alternatively, the acoustic sensor 162 may be (e.g.) fixed to the lower surface of the polishing layer 112 by an adhesive.

[0034] The acoustic sensor 162 can be connected to a power supply and / or other signal processing electronics 166 via a rotary coupler (e.g., a mercury slip ring) through a circuit system 168. The signal processing electronics 166 can then be connected to a controller 190.

[0035] The in-situ acoustic monitoring system 160 is a passive acoustic monitoring 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 kHz to 400 kHz or 200 kHz to 1 MHz. For example, to monitor the polishing of the inter-layer dielectric (ILD) in shallow trench isolation (STI), a frequency range of 225 kHz to 350 kHz can be monitored.

[0036] The signal from sensor 162 can be amplified by a built-in internal amplifier with a gain of 40–60 dB. If necessary, the signal from sensor 162 can then be further amplified and filtered (if necessary) and digitized via an A / D port to, for example, a high-speed data acquisition board in electronics 166. Data from sensor 162 can be recorded in the range of 1 MHz to 10 MHz, for example, 1 MHz to 3 MHz or 6 MHz to 8 MHz.

[0037] For sensor 162, a piezo-acoustic sensor capable of efficient high-frequency acoustic energy detection can be used.

[0038] In an example in which multiple slurry delivery channels 116 are formed in the top surface of the polishing layer 112 of the polishing pad 110, the aperture 138 can be aligned with the flat area between the channels 116, that is, the aperture 138 is not directly below the channel.

[0039] In this example, acoustic sensor 162 is positioned in platform 120 below aperture 138 to receive acoustic signals propagating through polished layer 112 from substrate 10.

[0040] An acoustic monitoring system 160 monitors sound waves generated during the polishing operation, wherein a sensor 162 travels along a path passing under the support head 140 and the substrate 10. (See now for further details.) Figure 2 A top view of platform 120 and supported polishing pad 110 is shown, wherein substrate 10 is constrained by retaining ring 142. During polishing operation, the relative movement between pad 110 and substrate 10 is generated by rotation of platform 120, movement of bearing head 140 constraining substrate 10, or a combination thereof. As platform 120 and supported pad 110 rotate about axis 125, sensor 162 relative to... Figure 2The visual reference frame follows path 102. When sensor 162 follows path 102, sensor 162 travels below the separation portion of ring assembly 142 and substrate 10. Path portion 306 corresponds to the case when sensor 162 is below substrate 10, and path portions 304 and 308 correspond to the case when sensor 162 is below retaining ring 142.

[0041] As the sensor 162 passes under the bearing head 140, the acoustic sensor 162 measures acoustic energy, such as the energy generated by the contact between the retaining ring 142 or the substrate 10 and the polishing pad 110 and the aperture 138. Specifically, the sensor 162 measures compressed sound waves passing through the polishing pad 110. The acoustic energy reaching the sensor 162 is primarily caused by friction between the polishing pad 110 (including the aperture 138) and specific components directly above the sensor 162 (e.g., the retaining ring 142 or the substrate 10). By analyzing the signal portion corresponding to the path portion 306, information about the interaction between the substrate 10 and the polishing pad 110 can be obtained.

[0042] An exemplary time-series acoustic signal 300 is illustrated, and represents the on-chip portion 306' of signal 300, corresponding to path portion 306. Reference Figure 2 and Figure 3 Acoustic monitoring system 160 (e.g., controller 190) processes acoustic signal 300 and subdivides it into multiple segments. Acoustic monitoring system 160 may subdivide acoustic signal 300 into multiple segments based on one or more signal parameters, such as the amplitude of acoustic signal 300. Some segments may correspond to portions of the signal that indicate abnormal acoustic events, such as portion 306'. Acoustic monitoring system 160 may monitor the amplitude of acoustic signal 300, the position of acoustic sensor 162, or both, to determine the presence and / or location of abnormal acoustic events.

[0043] In some implementations, the acoustic monitoring system 160 performs signal processing on the acoustic data generated by the acoustic sensor 162 to filter (e.g., denoise) the acoustic data before transmitting it to the controller 190. The filtering may be a low-pass filter or a running window averaging to smooth the measured signal from the sensor 162. In some instances, the acoustic monitoring system 160 generates an average of the measured signal 300 within each segment.

[0044] Occasionally, the acoustic signal 300 may include anomalous acoustic events, such as deviations from the expected form of the acoustic signal 300, which can be detected by the controller 190 based on the received acoustic signal 300 from the acoustic signal sensor 162. The detected anomalous acoustic events may correspond to one or more instances of anomalies, such as defects in the substrate 10 or anomalies in the polishing process. Other instances of anomalies include scratches on the polishing pad or wafer, vibration of the carrier head 140, interruption of the flow of polishing fluid 132, breakage of the substrate 10, lack of adjustment disc, presence of rinsing fluid, lack of rinsing fluid or pressure of the rinsing fluid, or improper detachment of the substrate 10 from the carrier head 140. Some of these instances will occur as anomalous acoustic events during monitoring when the sensor 162 is not under the carrier head 140.

[0045] Acoustic monitoring system 160 transmits acoustic signal 300 to controller 190. Controller 190 processes the received acoustic signal 300 to determine the presence of an anomalous acoustic event by comparing the values ​​of characteristics of signal 300 to predetermined thresholds. Examples of signal characteristics include the average amplitude of a segment of the signal, the maximum or minimum amplitude within a segment of the signal, the intensity at a frequency in the spectrum of the segment of the signal, the total power over a bandwidth of the spectrum of the segment of the signal, or the location (frequency) of a peak or trough in the spectrum of the segment of the signal. In some implementations, controller 190 determines alternative data parameters, such as the derivative, average, integral, standard deviation, or variance of acoustic signal 300 or one or more segments of acoustic signal 300. In some instances, controller 190 compares the received signal 300 with one or more stored test signals generated by the test substrate during different polishing processes. Test signals may have been previously determined to be free of anomalous acoustic events and are therefore considered successful polishing operations.

[0046] exist Figure 3 The diagram illustrates an exemplary time-series acoustic signal 400 (which may be an instance of signal 300) having an on-chip segment 406' determined by controller 190. Segment 406' is determined by controller 190 based on an average amplitude increase from the surrounding acoustic signal 400. On-chip segment 406' includes an exemplary anomalous acoustic event 402. Anomalous acoustic event 402 is a part of acoustic signal 400 and has a generally higher instantaneous and / or average amplitude than the surrounding acoustic signal 400, but may have different acoustic parameters when compared to acoustic signal 400.

[0047] In this example, the anomaly is an incorrect film stacking or an incorrect film type in substrate 10. Substrate 10 includes a series of sequentially deposited conductive, semiconductive, or insulating layers that appear on a silicon wafer in the expected order. If the deposited layers are incorrectly deposited out of order, partially deposited, or both, signal 300 may include an anomalous acoustic event corresponding to the incorrect film stacking.

[0048] In some instances, anomalous acoustic events can be identified at the start of polishing. For example, in cases of missing deposit layers or substantial errors in the deposition sequence, the difference is immediately detected as an anomalous acoustic event because the observed intensity is outside the normally observed range at the start of polishing. Other acoustic events can be detected later in the evolution of the signal.

[0049] In this example, the anomaly is a defect in substrate 10, such as a physical defect in substrate 10 (e.g., its surface) that adversely affects the form or function of substrate 10, such as scratches, cracks, fragments, missing portions of layers, or combinations thereof. A defect in substrate 10 may manifest as a signal segment with increased amplitude or increased power within a specific frequency range in the converted signal. A defect (e.g., a scratch) may be a temporary, single event, such as trapping a particle under substrate 10 for a single pass, or it may be a repeatable event, such as a continuous series of scratches.

[0050] Anomalies can be air bubbles (e.g., trapped or entrained gas) between the substrate 10 and the pad 110, which adversely affect the polishing process and reduce surface uniformity. Air bubbles can manifest as signal segments with increased amplitude, reduced power, or both within a specific frequency range.

[0051] Anomalies can be caused by poor pad rinsing transitions. At the end of the polishing process, substrate 10 is removed from contact with pad 110, and polishing liquid (e.g., slurry) is rinsed away from the surface of polishing layer 112. This process helps ensure a uniform slurry composition on a wafer-to-wafer basis and removes contaminants (such as particles) polished from the surface of substrate 10 to reduce defects. In one instance, unusual power amplitude or variance detected at one or more locations on the wafer indicates slurry rather than water, suggesting that some portions of the wafer contain a certain amount of slurry, for example, that has not been completely rinsed.

[0052] Generally, while the substrate 10 is held against the flexible film 144, the substrate 10 is removed from contact by lifting the support head 140. The rinsing arm 134 supplies rinsing liquid 136 to the outer polishing layer 112 and removes contaminated slurry. Once a sufficient amount of contaminated slurry (e.g., substantially all of the slurry) has been removed, the rinsing arm 134 stops supplying rinsing liquid 136.

[0053] refer to Figure 4 After the rinsing transition, the carrier head 140 brings the substrate 10 into contact with the pad 110. For clarity, dimensions are exaggerated; typically, the substrate 10 is in direct contact with the upper surface of the pad 110, and the rinsing liquid 136 and polishing liquid 132 form a thin liquid layer and reside in the slurry delivery tank 116. If the polishing liquid 132 is not sufficiently removed and some polishing liquid 132 remains between the substrate 10 and the outer polishing layer 112, this is referred to as a “poor pad rinsing transition,” which should be corrected before continuing the polishing process. Figure 4 The diagram illustrates both polishing fluid 132 and rinsing fluid 136 between substrate 10 and outer polishing layer 112, resulting in acoustic signals different from those present when polishing fluid 132 or rinsing fluid 136 is present. Poor liner rinsing transition can manifest as signal segments where the signal power spectrum fluctuates outside the expected boundaries. From this signal, controller 190 can determine that the fluid type present between substrate 10 and polishing layer 112 is an incorrect fluid type, for example, when polishing fluid 132 is present after liner rinsing.

[0054] The controller 190 may store in memory or an attached storage component a catalog (e.g., a table or index) of anomalies detectable by the in-situ acoustic monitoring system 160. Additionally, for each detectable anomaly, the controller 190 stores one or more associated criteria (e.g., a spectrum representing the spectrum for which the corresponding anomaly occurs). The controller 190 processes the acoustic signal 300 to identify the presence of one or more anomalies. For example, the controller 190 compares the determined anomalous acoustic event with a detectable anomaly entry in the catalog. In one instance, the controller 190 processes the acoustic signal 300 to generate a detected spectrum and compares it with a stored anomalous spectrum. If the detected spectrum sufficiently matches the criteria for anomalous spectra stored in the catalog, the controller 190 determines the presence of the associated anomaly. The controller 190 may then control the device 100 in response to the determination, including conveying one or more warnings for display to a user, terminating the polishing process, or a combination thereof.

[0055] Criteria associated with anomalies can be determined experimentally. For example, polishing one or more test wafers that may include known anomalies, detecting the current anomaly based on received signals that deviate from baseline signals received from test wafers known to be defect-free or anomaly-free, and recording differences in the received signals to determine the type of anomaly with associated differences.

[0056] This article discloses Figure 5 Method 500 for polishing and acoustic monitoring to detect anomalies.

[0057] The surface of the substrate is brought into contact with the polished surface of the polishing pad (step 502). The substrate 10 is provided and mounted (e.g., clamped) to the carrier head. The carrier head brings the surface of the substrate into contact with the polished surface (e.g., the polished layer 112 of the polishing pad).

[0058] Movement is generated between the substrate and the polishing pad (step 504). For example, the polishing pad is supported by a rotatable platform (e.g., platform 120) configured to rotate about a central axis of rotation (e.g., axis 125). In some instances, the carrier head may also rotate about a central axis of rotation (e.g., central axis 155), which, when the carrier head rotates, can induce rotation of the substrate. The relative movement of the carrier head and / or platform generates relative movement between the substrate and the pad.

[0059] A liquid slurry (e.g., polishing liquid 132) is provided to the polishing surface (step 506). The liquid slurry is supplied to the polishing surface through a liquid slurry port (e.g., port 130), and in some instances, the liquid slurry may be heated and / or cooled before being supplied.

[0060] Acoustic energy is monitored by a sensor of the acoustic monitoring system (e.g., sensor 162 of acoustic monitoring system 160) (step 508). The sensor may be mounted in a recess of the platform and receive the generated acoustic signals through polished layer 112.

[0061] The controller receives signals representing acoustic energy from sensors in the acoustic monitoring system (step 510). As the acoustic sensors travel beneath the substrate, the received acoustic signals indicate the polishing process and may include information about the liquid between the substrate and the pad. The controller performs one or more processes to determine whether there are any anomalous acoustic events in the received acoustic signals.

[0062] The controller determines the presence of an abnormal acoustic event based on the received acoustic signal (step 512), such as abnormal acoustic event 402. The controller performs signal processing to determine the presence of the abnormal acoustic event, such as determining the average amplitude, maximum or minimum amplitude, intensity at a certain frequency in the spectrum, total power, or the location (frequency) of a peak or valley in the spectrum. The controller may determine alternative data parameters, such as the derivative, average, integral, standard deviation, or variance of the acoustic signal, to determine the presence of the abnormal acoustic event. Abnormal acoustic events may indicate anomalies in the polishing process.

[0063] The controller identifies the type of anomalous acoustic event based on the anomalous acoustic event (step 514). The controller includes a catalog of anomalous acoustic event types, which associates each type of anomalous acoustic event with one or more associated anomalous events in the polishing process. Examples of anomalous events in the polishing process include bubbles between the substrate and the polishing layer, poor rinsing transitions, or inappropriate film types exposed on the substrate surface. Each anomalous event may correspond to a different type of identified anomalous acoustic event.

[0064] Warnings can be generated based on the determination of the presence of abnormal acoustic events. Examples of warnings that the device can generate include text-based messages or audio / visual cues delivered to local or networked devices such as monitors or computers.

[0065] Based on the presence of abnormal acoustic events or the identified type of anomaly, the substrate can be removed from contact with the polished surface. In one example, the anomaly is a poor gasket flushing transition; the controller commands the carrier head to remove the substrate from contact with the polished surface and commands the flushing supply arm to supply flushing fluid to the gasket. In another example, the anomaly is improper membrane stacking; the controller generates a warning and commands the carrier head to remove the substrate from contact with the gasket.

[0066] In some instances, the anomaly is the presence of used paste prior to the initiation of a new polishing step. Used paste present on a new substrate before the start of a new polishing step can negatively impact the polishing process due to particles from the previously polished paste. Therefore, detecting the presence of used paste promotes performing a rinsing step before starting a new polishing process.

[0067] If used slurry is detected, the rinsing arm 134 applies rinsing liquid 136 once or multiple times until the controller 190 determines that the used slurry is no longer present on the polishing layer 112.

[0068] While this specification contains numerous details, these should not be construed as limiting the scope that can be claimed, but rather as descriptions of features specific to particular instances. Certain features described in this specification in the context of individual implementations may also be combined. Conversely, the various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple embodiments.

Claims

1. A chemical mechanical polishing apparatus, comprising: Platform, which is used to support the polishing pad; A support head, used to hold the surface of the substrate against the polishing pad; A motor for generating relative motion between the platform and the support head in order to polish the overlay on the substrate; An in-situ acoustic monitoring system, comprising an acoustic sensor that receives acoustic energy from the substrate and the polishing pad; as well as Controller, the controller is configured to Detecting abnormal acoustic events based on measurements from the in-situ acoustic monitoring system, and The type of anomaly is determined based on the signals measured by the in-situ acoustic monitoring system during the anomalous acoustic event.

2. The device of claim 1, wherein the controller detects the anomalous acoustic event based on a comparison of the signal with a previous measurement of an acoustic signal generated by friction between the test substrate and the polishing pad.

3. The device of claim 1, wherein the detection of the anomalous acoustic event is based on the controller determining the power spectrum of the acoustic signal; determining the difference between the power spectrum and a reference power spectrum stored in a storage component of the device; and detecting the anomalous acoustic event based on the difference.

4. The device of claim 1, wherein the controller is configured to store a catalog including a plurality of exception types and at least one criterion for each exception type.

5. The device of claim 4, wherein the at least one criterion includes similarity to a reference spectrum representing the anomaly type.

6. The device of claim 5, wherein the controller is configured to store different reference spectra for each different anomaly type.

7. The device of claim 4, wherein the type of anomaly includes at least one of the following: scratches on the surface of the substrate, unintended film type, poor pad flushing transition, or air bubbles between the substrate and the polishing pad.

8. The device of claim 7, wherein the anomaly type includes an unexpected membrane type, and the determination is based on comparing the acoustic signal with a previous measurement of an acoustic signal generated by a test substrate including an expected membrane type and the polishing pad.

9. The device of claim 7, wherein the type of anomaly includes a poor liner flushing transition.

10. The device of claim 7, wherein the type of anomaly includes air bubbles between the substrate and the polishing pad.

11. The device of claim 1, wherein the acoustic sensor is disposed within a recess in the top surface of the platform.

12. A chemical mechanical polishing apparatus, comprising: Platform, which is used to support the polishing pad; A support head, used to hold the surface of the substrate against the polishing pad; A motor for generating relative motion between the platform and the support head in order to polish the overlay on the substrate; A polishing liquid source, the polishing liquid source being used to deliver polishing liquid to the polishing pad; A rinsing liquid source is provided for delivering rinsing liquid to the polishing pad; An in-situ acoustic monitoring system, comprising an acoustic sensor that receives acoustic energy from the substrate and the polishing pad; as well as A controller configured to detect poor liner flushing transitions based on measurements from the in-situ acoustic monitoring system.

13. A chemical mechanical polishing apparatus, comprising: Platform, which is used to support the polishing pad; A support head, used to hold the surface of the substrate against the polishing pad; A motor for generating relative motion between the platform and the support head in order to polish the overlay on the substrate; A polishing liquid source, the polishing liquid source being used to deliver polishing liquid to the polishing pad; An in-situ acoustic monitoring system, comprising an acoustic sensor that receives acoustic energy from the substrate and the polishing pad; as well as A controller configured to detect air bubbles in the polishing liquid between the substrate and the polishing pad.

14. A polishing method, comprising the following steps: Make the surface of the substrate come into contact with the polishing surface of the polishing pad; Relative motion is generated between the substrate and the polishing pad; The liquid slurry is provided to the polishing surface of the polishing pad; The acoustic energy from the substrate and the polishing pad is monitored using an in-situ acoustic monitoring system including acoustic sensors; The presence of abnormal acoustic events is determined based on signals from the acoustic sensors. as well as The type of anomaly is identified based on acoustic signals from the in-situ acoustic monitoring system during the anomalous acoustic event.

15. The method of claim 14, further comprising the following steps: A warning is generated based on the determination of the existence of the abnormal acoustic event.

16. The method of claim 14, further comprising the following steps: Based on the determination of the presence of the anomalous acoustic event or the identified anomalous type, the surface of the substrate is removed from contact with the polished surface.

17. The method of claim 14, further comprising the following steps: The type of the anomaly was identified as a poor liner flushing transition.

18. The method of claim 14, further comprising the following steps: The type of the anomaly is identified as inappropriate membrane stacking.

19. The method of claim 14, further comprising the following steps: The anomaly was identified as an air bubble between the substrate and the polishing pad.

20. The method of claim 14, further comprising the following steps: The surface of the substrate is removed from contact with the polished surface based on the type of the anomaly.

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