Chemical mechanical polishing apparatus and method utilizing acoustic monitoring for process reliability

Abstract

This article discloses a chemical mechanical polishing apparatus, including a platform for supporting a polishing pad; a support head for holding the surface of a substrate 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 that receive 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.

Description

Technical Field

[0001] The present disclosure relates to chemical mechanical polishing, and more particularly to detecting abnormal events from acoustic signals received during chemical mechanical polishing. Prior Art

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconductive, 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. 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, the portions of the conductive layer remaining between the raised patterns in the insulating layer form vias, plugs, and lines, which 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 remains on the non-planar surface. Furthermore, lithography often requires planarization of the substrate surface.

[0003] Chemical mechanical polishing (CMP) is a well-established planarization method. This method typically requires mounting a substrate on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head applies a controllable load to the substrate, pushing it against the polishing pad. An abrasive polishing slurry is typically applied to the surface of the polishing pad.

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

[0005] In one aspect, a chemical mechanical polishing apparatus includes a carrier head for holding a substrate against a polishing pad. An in-situ acoustic monitoring system receives acoustic signals from the substrate and the carrier 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 an alert based on the detected anomalies.

[0006] Generally, aspects disclosed herein are directed to a chemical mechanical polishing apparatus comprising a platform for supporting a polishing pad; a carrier head for holding a surface of a substrate against the polishing pad; a motor for generating relative motion between the platform and the carrier head to polish an overlying layer on the substrate; an in-situ acoustic monitoring system comprising an acoustic sensor for receiving acoustic energy from the substrate and the polishing pad; and a controller configured to detect an abnormal acoustic event based on measurements from the in-situ acoustic monitoring system and to determine a 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 an abnormal acoustic event based on a comparison of the signal with previous measurements of an acoustic signal generated by friction between a test substrate and a polishing pad. Detection of the abnormal acoustic event may be based on the controller determining a power spectrum of the acoustic signal; determining a difference between the power spectrum and a reference power spectrum stored in a storage element of the apparatus; and detecting the abnormal acoustic event based on the difference. The controller may be configured to store a directory that may include a plurality of anomaly types and at least one criterion for each anomaly type. The at least one criterion may include a similarity to a reference spectrum representative of the anomaly type. The controller may be configured to store a different reference spectrum for each different anomaly type. The anomaly type may include at least one of a scratch on the substrate surface, an unexpected film type, a poor pad rinse 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 previous measurements of an acoustic signal generated by a test substrate (which may include an expected film type) and a polishing pad. The anomaly type may include a poor pad rinse transition. Such anomalies may include air bubbles between the substrate and the polishing pad.The acoustic sensor may be disposed within a recess in the top surface of the platform.

[0008] Generally, aspects disclosed herein are chemical mechanical polishing apparatus comprising a platform for supporting a polishing pad; a carrier head for holding a surface of a substrate against the polishing pad; a motor for generating relative motion between the platform and the carrier head to polish an overlying layer on the substrate; a polishing liquid source for delivering a polishing liquid onto the polishing pad; a rinse liquid source for delivering a rinse liquid onto the polishing pad; an in-situ acoustic monitoring system comprising an acoustic sensor for receiving acoustic energy from the substrate and the polishing pad; and a controller configured to detect a poor pad rinse transition based on measurements from the in-situ acoustic monitoring system.

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

[0010] Generally, disclosed herein is 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 onto 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 an acoustic sensor; determining the presence of an abnormal acoustic event based on a signal from the acoustic sensor; and identifying a type of abnormality based on an acoustic signal from the in-situ acoustic monitoring system during the abnormal acoustic event.

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

[0012] Real-time passive monitoring of acoustic signals facilitates the detection of anomalies in the acoustic emission signal, which can reduce production losses due to poor-quality substrates with scratches due to poor pad rinse transitions. 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 facilitates differentiation between detected expected and unexpected events, thereby improving production efficiency and reducing losses.

[0014] The details of one or more embodiments are set forth in the accompanying drawings and the following description. Other aspects, features, and advantages will be apparent from the description and drawings, as well as from the claims. Simple diagram description

[0015] FIG. 1 is a schematic side view of a polishing system including an in-situ acoustic monitoring system.

[0016] FIG. 2 is a schematic top view illustration of a substrate being polished on a polishing pad with an example path followed by an acoustic sensor during a polishing operation and an example acoustic signal generated as the sensor moves along the example path.

[0017] FIG. 3 is a diagram of an example acoustic signal and the segments corresponding to the signal received from beneath a substrate.

[0018] FIG. 4 is an illustration of a poor liner rinse transition during planarization of a substrate surface.

[0019] FIG. 5 is a flow chart of a polishing method including detecting abnormal events from acoustic signals.

[0020] In the drawings, like reference numerals indicate like elements. Implementation Method

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

[0022] Another issue is the lack of real-time or on-tool means to detect these adverse process events during the wafer polishing process. Furthermore, existing solutions that rely on optical metrology of the wafer surface are expensive and require costly upgrades to existing systems. Compared to optical-based solutions, passive acoustic monitoring systems can reduce the costs associated with real-time monitoring and reduce the complexity and maintenance requirements of existing systems.

[0023] FIG1 illustrates an example of a polishing apparatus 100. The polishing apparatus 100 includes a rotatable, dish-shaped platform 120 on which a polishing pad 110 is positioned. 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) may rotate a drive shaft 124 to rotate the platform 120.

[0024] The polishing apparatus 100 may include a port 130 to dispense 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 so as to maintain the polishing pad 110 in a uniformly abrasive state.

[0025] The polishing apparatus 100 can include a rinse arm 134 to dispense a rinse liquid 136, such as water, onto the polishing pad 110. The rinse liquid 136 is dispensed between polishing events to remove the polishing liquid 132 from the polishing layer 112. In some examples, the rinse liquid 136 is dispensed under high pressure and / or temperature-conditioned (e.g., heated or cooled) before being dispensed onto 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 can have independent control over polishing parameters (eg, 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, therefore, to the substrate 10. Although only three chambers are shown in FIG. 1 , there may be one or two chambers, or four or more chambers, such as five chambers.

[0028] The carrier heads 140 are suspended from a support structure 150 (e.g., a turntable or track) and are connected to a carrier head rotation motor 154 (e.g., a DC induction motor) via a drive shaft 152, which allows the carrier heads to rotate about an axis 155. Optionally, each carrier head 140 can oscillate laterally (e.g., on a slider on the structure 150), either by rotation of the turntable itself, or by sliding along the track. In typical operation, the platform rotates about its central axis 125, and each carrier 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 the motors 121 and 154 to control the rotational speed of the platform 120 and the carrier head 140. For example, each motor may include an encoder that measures the rotational speed of the associated drive shaft. Feedback control circuitry (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 (e.g., an optical interrupter or a rotary encoder attached to the platform rim) can be used to determine the angular position of the platform 120. This allows the acoustic signal, or portion of the signal, to be recorded when the sensor 162 is close to the substrate (e.g., when the sensor 162 is below 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 of which generates a signal, such as a digital or analog signal, representing an acoustic waveform received at the sensor. If multiple acoustic sensors are present, the acoustic sensors can be mounted at different locations on the upper platform 120, for example, at equal angular intervals around the rotational axis of the platform 120.

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

[0033] In the implementation shown in FIG. 1 , the acoustic sensor 162 is positioned in a recess 164 in the platform 120 and is positioned to receive acoustic energy from the side of the substrate closer to the polishing pad 110. As shown in FIG. 1 , the acoustic sensor 162 can 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 implementations, the acoustic sensor 162 is biased against the polishing layer 112, for example, by a spring. Alternatively, the acoustic sensor 162 can be secured to the lower surface of the polishing layer 112, for example, by an adhesive.

[0034] The acoustic sensor 162 may be connected to a power supply and / or other signal processing electronics 166 via a rotary coupler (eg, a mercury slip ring) via circuitry 168. The signal processing electronics 166 may in turn 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 may 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 inter-layer dielectric (ILD) in shallow trench isolation (STI), a frequency range of 225 kHz to 350 kHz may 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 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 the sensor 162, a piezoelectric acoustic sensor capable of efficient high-frequency acoustic energy detection may be used.

[0038] In examples where a plurality of slurry delivery grooves 116 are formed in the top surface of the polishing layer 112 of the polishing pad 110 , the apertures 138 can be aligned with the flat areas between the grooves 116 , ie, the apertures 138 are not directly beneath the grooves.

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

[0040] Acoustic monitoring system 160 monitors acoustic waves generated during polishing operations, with sensor 162 traversing a path beneath carrier head 140 and substrate 10. Referring now to FIG. 2 , a top view of platform 120 and supported polishing pad 110 is shown, with substrate 10 constrained by retaining ring 142. During polishing operations, relative motion between pad 110 and substrate 10 is generated by rotation of platform 120, movement of carrier head 140 constraining substrate 10, or a combination thereof. As platform 120 and supported pad 110 rotate about axis 125, sensor 162 follows path 102 relative to the visual reference frame of FIG. 2 . As sensor 162 follows path 102, it travels beneath a separate portion of ring assembly 142 and substrate 10. Path portion 306 corresponds to when sensor 162 is beneath substrate 10, and path portions 304 and 308 correspond to when sensor 162 is beneath retaining ring 142.

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

[0042] An exemplary time-series acoustic signal 300 is shown inset, representing an on-wafer portion 306' of the signal 300, corresponding to the path portion 306. Referring to Figures 2 and 3, the acoustic monitoring system 160 (e.g., the controller 190) processes the acoustic signal 300 and subdivides it into segments. The acoustic monitoring system 160 may subdivide the acoustic signal 300 into segments based on one or more signal parameters, such as the amplitude of the acoustic signal 300. Some segments may correspond to portions of the signal that indicate an abnormal acoustic event, such as portion 306'. The acoustic monitoring system 160 may monitor the amplitude of the acoustic signal 300, the position of the acoustic sensor 162, or both, to determine the presence and / or location of the abnormal acoustic event.

[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., remove noise) the acoustic data before communicating it to the controller 190. The filtering may be a low-pass filter or a running window average to smooth the measured signal from the sensor 162. In some examples, the acoustic monitoring system 160 generates an average of the measured signal 300 within each segment.

[0044] Occasionally, the acoustic signal 300 includes an abnormal acoustic event, e.g., a deviation 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 abnormal acoustic event may correspond to one or more instances of an anomaly, such as a defect in the substrate 10 or an anomaly in the polishing process. Other examples of anomalies include scratches on the polishing pad or wafer, vibration of the carrier head 140, interrupted flow of the polishing liquid 132, substrate 10 breakage, a missing conditioning disk, the presence of rinse liquid, the absence of rinse liquid or the pressure of the rinse liquid, or improper removal of the substrate 10 from the carrier head 140. Some of these instances will appear as abnormal acoustic events during monitoring when the sensor 162 is not beneath the carrier head 140.

[0045] Acoustic monitoring system 160 transmits acoustic signal 300 to controller 190. Controller 190 processes received acoustic signal 300 to determine the presence of an abnormal acoustic event by comparing the value of a characteristic of signal 300 to a predetermined threshold. 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 certain frequency within the segment spectrum of the signal, the total power within a certain bandwidth of the segment spectrum of the signal, or the location (frequency) of a peak or valley within the segment spectrum of the signal. In some implementations, controller 190 determines a proxy data parameter, such as the derivative, mean, integral, standard deviation, or variance of acoustic signal 300 or one or more segments of acoustic signal 300. In some examples, controller 190 compares received signal 300 to one or more stored test signals generated by test substrates during different polishing processes. The test signal may have been previously determined to be free of abnormal acoustic events and therefore considered a successful polishing operation.

[0046] FIG3 shows an exemplary time-series acoustic signal 400 (which may be an example of signal 300) having an on-wafer 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-wafer segment 406′ includes an exemplary abnormal acoustic event 402. Abnormal acoustic event 402 is a portion of acoustic signal 400 that has an instantaneous and / or average amplitude that is substantially higher than the surrounding acoustic signal 400, although other abnormal acoustic events may have different acoustic parameters when compared to acoustic signal 400.

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

[0048] In some cases, anomalous acoustic events can be identified at the start of polishing. For example, in the case of a missing deposition layer or a substantial deposition sequence error, the observed intensity at the start of polishing is outside the typically observed range, and thus the difference is immediately detected as an anomalous acoustic event. Other acoustic events can be detected later in the evolution of the signal.

[0049] In an example, an anomaly is a defect in the substrate 10, such as a physical defect in the substrate 10 (e.g., a surface) that adversely affects the form or function of the substrate 10, such as a scratch, crack, chip, missing layer portion, or a combination thereof. A defect in the substrate 10 may manifest as a signal segment with increased amplitude or increased power within a specific frequency range in the conversion signal. A defect (e.g., a scratch) may be a transient, single event, such as a particle trapped under the substrate 10 for a single pass, or may be a reproducibly detectable event, such as a continuous series of scratches.

[0050] Anomalies may be bubbles (e.g., trapped or entrained gases) between the substrate 10 and the pad 110, which adversely affect the polishing process and reduce surface uniformity. Bubbles may appear as signal segments with increased amplitude, decreased power, or both within a specific frequency range.

[0051] The anomaly can be a poor pad rinse transition. At the end of the polishing process, substrate 10 is removed from contact with pad 110, and the polishing liquid (e.g., slurry) is rinsed 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 example, unusual power amplitude or variance detected at one or more locations on the wafer indicates slurry rather than water, indicating that some portions of the wafer contain a certain amount of slurry, for example, that was not fully rinsed.

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

[0053] Referring to FIG. 4 , the carrier head 140 brings the substrate 10 into contact with the pad 110 after a rinse transition. Dimensions are exaggerated for clarity. Typically, the substrate 10 is in direct contact with the upper surface of the pad 110, and the rinse 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 adequately removed and some remains between the substrate 10 and the outer polishing layer 112, this is referred to as a "bad pad rinse transition" and should be corrected before continuing the polishing process. FIG. 4 shows both the polishing liquid 132 and the rinse liquid 136 between the substrate 10 and the outer polishing layer 112, resulting in an acoustic signal that differs from when either the polishing liquid 132 or the rinse liquid 136 is present. A bad pad rinse transition can manifest as signal segments where the signal power spectrum fluctuates outside expected boundaries. From this signal, the controller 190 may determine that the type of liquid present between the substrate 10 and the polishing layer 112 is an incorrect type of liquid, such as when the polishing liquid 132 is present after a pad rinse.

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

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

[0056]

[0054] Disclosed herein is a method 500 for polishing and acoustic monitoring to detect anomalies in FIG. 5.

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

[0058] Motion 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 examples, the carrier head can also rotate about a central axis of rotation (e.g., central axis 155), which can induce rotation of the substrate as the carrier head rotates. The relative motion of the carrier head and / or platform generates relative motion between the substrate and the pad.

[0059] A liquid slurry (eg, polishing liquid 132) is provided to the polishing surface (step 506). A liquid slurry port (eg, port 130) provides the liquid slurry to the polishing surface, and in some examples, the liquid slurry may be heated and / or cooled before being provided.

[0060] The acoustic energy is monitored by a sensor of the acoustic monitoring system (eg, 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 signal through the polishing layer 112 .

[0061] A controller receives a signal representing acoustic energy from a sensor of an acoustic monitoring system (step 510). As the acoustic sensor travels beneath the substrate, the received acoustic signal indicates the polishing process and may include information about the fluid between the substrate and the pad. The controller executes one or more processes to determine whether an anomalous acoustic event is present in the received acoustic signal.

[0062] The controller determines the presence of an abnormal acoustic event, such as abnormal acoustic event 402, based on the received acoustic signal (step 512). 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 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, mean, integral, standard deviation, or variance of the acoustic signal, to determine the presence of the abnormal acoustic event. The abnormal acoustic event may indicate an anomaly in the polishing process.

[0063] The controller identifies a type of anomaly based on the abnormal acoustic event (step 514). The controller includes a catalog of types of abnormal acoustic events, associating each type of abnormal acoustic event with one or more associated anomalies in the polishing process. Example anomalies in the polishing process include air bubbles between the substrate and the polishing layer, poor rinse transitions, or an inappropriate film type exposed on the substrate surface. Each anomaly may correspond to a different type of determined abnormal acoustic event.

[0064] An alert can be generated based on a determination of the presence of an abnormal acoustic event. Examples of alerts that the device can generate include text-based messages or audio / visual prompts transmitted to a local or networked device (such as a monitor or computer).

[0065] Based on the presence of an abnormal acoustic event or the type of abnormality identified, the substrate can be removed from contact with the polishing surface. In one example, the type of abnormality is a poor pad rinse transition, and the controller commands the carrier head to remove the substrate from contact with the polishing surface and commands the rinse supply arm to provide rinse liquid to the pad. In another example, the type of abnormality is an improper film stack, and the controller generates a warning and commands the carrier head to remove the substrate from contact with the pad.

[0066] In some instances, the anomaly is the presence of slurry prior to initiating a new polishing step. The presence of used slurry prior to initiating a new polishing step on a new substrate can negatively impact the polishing process due to the presence of particles in the slurry from the previous polish. Therefore, detecting the presence of used slurry facilitates performing a rinse step prior to starting a new polishing step.

[0067] If used slurry is detected, the rinse arm 134 dispenses the rinse liquid 136 one or more times until the controller 190 determines that used slurry is no longer present on the polishing layer 112 .

[0068] While this specification contains many specifics, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features described in this specification in the context of separate implementations may also be combined. Conversely, various features described in the context of a single implementation can also be implemented in multiple embodiments separately or in any suitable subcombination.

[0069] 10:Substrate 100: Polishing equipment 102: Path 110: Polishing pad 112: polishing layer 114: backing layer 116: Slurry conveying trough 120: Platform 121: Motor 124: Drive shaft 125: Axis 130: Port 132: Polishing liquid 134:Flush arm 136: Flushing liquid 138: Pore 140: Bearing head 142: Fixed ring 144: Flexible membrane 146a: Chamber 146b: Chamber 146c: Chamber 150:Structure 152: Drive shaft 154: Motor 155: Central axis 160:Acoustic Monitoring System 162:Sensor 162 / 138: Sensor / Aperture 164: concave part 166: Electronic devices 168: Circuit System 190:Controller 300: Acoustic signal 304: Path part 306: Path part 306': Part 308: Path part 400: Acoustic signal 402: Anomalous Acoustic Event 406': Segment 500:Method 502: Steps 504: Steps 506: Steps 508: Steps 510: Steps 512: Steps 514: Steps

[0070] Domestic storage information (please note the order of storage institution, date, and number) none Overseas deposit information (please note the order of deposit country, institution, date, and number) none

Claims

1. A chemical mechanical polishing apparatus, comprising: A platform to support a polishing pad; A support head is used to hold a surface of a substrate against the polishing pad; A motor for generating relative motion between the platform and the bearing head to polish an overlay 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 subdivide an acoustic signal measured by the in-situ acoustic monitoring system into a plurality of segments, detect an anomalous acoustic event based on at least one segment of the acoustic signal measured by the in-situ acoustic monitoring system, and determine an anomalous type based on at least one segment of the acoustic signal measured by the in-situ acoustic monitoring system during the anomalous acoustic event.

2. The device as claimed in 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 as claimed in claim 1, wherein the detection of the anomalous acoustic event is based on the controller determining a power spectrum of the acoustic signals; determining a difference between the power spectrum and a reference power spectrum stored in a storage element of the device; and detecting the anomalous acoustic event based on the difference.

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

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

6. The device as claimed in claim 5, wherein the controller is configured to store a different reference spectrum for each different anomaly type.

7. The apparatus as claimed in claim 4, wherein the types of anomalies include at least one of a scratch on the surface of the substrate, an unexpected film type, a poor pad flushing transition, or an air bubble between the substrate and the polishing pad.

8. The device as claimed in claim 7, wherein the anomaly types include an unexpected membrane type, and the determination is based on comparing the acoustic signals with previous measurements of acoustic signals generated by a test substrate including an expected membrane type and the polishing pad.

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

10. The device as claimed in claim 7, wherein the anomaly type includes an air bubble between the substrate and the polishing pad.

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

12. The apparatus as claimed in claim 1, wherein the detected anomalous acoustic event corresponds to an anomaly in the chemical mechanical polishing apparatus.

13. A chemical mechanical polishing apparatus, comprising: A platform to support a polishing pad; A support head is used to hold a surface of a substrate against the polishing pad; A motor is used to generate relative movement between the platform and the support head in order to polish an overlay on the substrate; A polishing liquid source for delivering a polishing liquid to the polishing pad; a rinsing liquid source for delivering a rinsing liquid to the polishing pad; and 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 subdivide an acoustic signal measured by the in-situ acoustic monitoring system into a plurality of segments, and to detect a defective liner flushing transition based on at least one of the plurality of segments.

14. A chemical mechanical polishing apparatus, comprising: A platform to support a polishing pad; A support head is used to hold a surface of a substrate against the polishing pad; A motor is used to generate relative movement between the platform and the support head in order to polish an overlay on the substrate; A polishing liquid source for delivering a polishing liquid to the polishing pad; 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 subdivide an acoustic signal measured by the in-situ acoustic monitoring system into a plurality of segments, and to detect an air bubble in the polishing liquid between the substrate and the polishing pad based on at least one of the plurality of segments.

15. A polishing method comprising the steps of: 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 an acoustic sensor; subdividing an acoustic signal measured by the acoustic sensor into a plurality of segments; determining the presence of an anomalous acoustic event based on at least one segment of the acoustic signal measured by the acoustic sensor; and identifying a type of anomalous event based on at least one segment of the acoustic signal from the in-situ acoustic monitoring system during the anomalous acoustic event.

16. The method as described in claim 15 further includes the step of: generating a warning based on the determination of the presence of the anomalous acoustic event.

17. The method as described in claim 15 further includes the step of: removing the surface of the substrate from contact with the polished surface based on the determination of the presence of the anomalous acoustic event or the identified type of anomalousness.

18. The method as described in claim 15 further includes the step of: identifying the type of the anomaly as a defective liner flushing transition.

19. The method as described in claim 15 further includes the step of: identifying the type of the anomaly as an inappropriate membrane stack.

20. The method as described in claim 15 further includes the step of: identifying the type of the anomaly as an air bubble between the substrate and the polishing pad.

21. The method as described in claim 15 further includes the step of removing the surface of the substrate from contact with the polished surface based on the type of the anomaly.

22. The method as described in claim 15, wherein the determined presence of the anomalous acoustic event corresponds to an anomaly in a chemical mechanical polishing apparatus.

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