Acoustic Carrier Head Monitoring

Abstract

The chemical mechanical polishing apparatus includes a platen for supporting a polishing pad, a carrier head including a rigid housing configured to hold a surface of a substrate against the polishing pad, a motor for generating relative motion between the platen and the carrier head to polish the substrate, an in-situ carrier head monitoring system including a sensor positioned to interact with the housing and to detect vibratory motion of the housing and generate a signal based on the detected vibratory motion, and a controller configured to generate a value for a carrier head status parameter based on the signal received from the in-situ carrier head monitoring system and to modify a polishing parameter or generate an alert based on the carrier head status parameter.

Description

[Technical field]

[0001]

[0001] The present disclosure relates to chemical mechanical polishing, and more particularly, to determining polishing parameters from signals received based on displacement of a carrier head during chemical mechanical polishing. [Background technology]

[0002]

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

[0003]

[0003] Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate, forcing it against the polishing pad. A polishing abrasive slurry is typically supplied to the surface of the polishing pad.

[0004]

[0004] The carrier head provides a controllable load to the substrate, forcing it against the polishing pad. Some carrier heads include a housing that is attached to the drive shaft and a gimbal mechanism that allows the base of the carrier head to be gimbaled relative to the housing and drive shaft while preventing lateral movement of the base. Summary of the Invention

[0005]

[0005] Disclosed herein is a chemical mechanical polishing apparatus that includes a carrier head for holding a substrate against a polishing pad. Relative motion occurs between the polishing pad and the carrier head to polish an exposed surface of the substrate. The apparatus includes an in-situ head monitoring system that receives a vibration signal from the carrier head (e.g., from the housing or from the gimbal). The head monitoring system generates and transmits a signal from the carrier head to a controller. The controller receives the vibration signal and generates a carrier head status parameter based on the signal. The controller is configured to modify one or more polishing parameters or generate an alert based on the carrier head status parameter.

[0006] In one aspect, a chemical mechanical polishing apparatus includes a platen for supporting a polishing pad, a carrier head including a rigid housing configured to hold a surface of a substrate against the polishing pad, a motor for generating relative motion between the platen and the carrier head to polish the substrate, an in-situ carrier head monitoring system including a sensor positioned to interact with the housing and to detect vibratory motion of the housing and generate a signal based on the detected vibratory motion, and a controller. The controller is configured to generate a value for a carrier head status parameter based on the signal received from the in-situ carrier head monitoring system, and to modify a polishing parameter or generate an alert based on the carrier head status parameter.

[0007]

[0007] In another aspect, a polishing method includes using a carrier head to hold a substrate against a polishing surface of a polishing pad, generating relative motion between the substrate and the polishing pad, monitoring vibrational motion of the carrier head with an in situ head monitoring system and generating a signal based on the motion, generating a value for a carrier head status parameter based on the signal from the in situ carrier head monitoring system, and altering polishing parameters or generating an alert based on the determined carrier head status parameter.

[0008]

[0008] Implementations may optionally include one or more of the following advantages: Reliable endpoint control is achieved because the polishing rate can be determined or a polishing rate determined by a separate monitoring system can be verified. Similarly, reliable system control is achieved because the value of a control parameter (such as rotation speed, pressure, etc.) can be determined or a rate of a control parameter value determined by a technique can be verified. Impending system failure can be detected and corrective action can be taken before an actual failure occurs.

[0009]

[0009] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a system diagram of a polishing system including an in-situ acoustic monitoring system. [Diagram 2]

[0011] FIG. 2 is a diagram of a carrier head having a head monitoring system. [Diagram 3] FIG. 2 is a diagram of a carrier head having a head monitoring system. [Figure 4A] FIG. 2 is a diagram of a carrier head having a head monitoring system. [Figure 4B]

[0012] FIG. 1 is a schematic diagram of distortion forces in a gimbal mechanism. [Figure 4C] FIG. 1 is a schematic diagram of distortion forces in a gimbal mechanism. [Diagram 5]

[0013] FIG. 2 is a flow chart diagram of an exemplary method of a polishing process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011]

[0014] In the drawings, like reference numbers indicate like elements.

[0012]

[0015] During the polishing process, the carrier head moves in a path where the retaining ring and substrate interact with the polishing layer of the polishing pad. The polishing results (e.g., layer thickness, or layer uniformity) can vary based on at least the frictional contact between the surfaces and various other polishing parameters, such as zone pressure, platen speed, head type, or conditioning recipe.

[0013]

[0016] Chemical mechanical polishing can present a variety of problems, and the techniques described herein can address any one or more of these problems, either independently or in conjunction.

[0014]

[0017] One of the problems in CMP is to determine the polishing rate of the layer being polished. Various techniques can be used, such as optical monitoring or eddy current monitoring. Generally, these monitoring techniques generate a value that represents thickness. The polishing rate can be calculated by monitoring a series of thickness measurements over time and determining the slope of a line fit to the measurements. However, these techniques require the accumulation of sufficient data, which is time consuming to detect changes in the polishing rate, and require a moderately complex monitoring system.

[0015]

[0018] However, if the vibration signal is correlated with the polishing rate, the polishing rate determined from the vibration signal can serve as validation of another monitoring system or can make other monitoring techniques (e.g., eddy current or optical) unnecessary.

[0016]

[0019] Another problem in CMP is verifying that the polishing system is operating at the desired control parameters (e.g., the desired rotation speed or chamber pressure). Ideally, the appropriate physical components (e.g., motors or pressure regulators) are simply operated by a controller according to a recipe with the desired control parameter values. In reality, however, the actual values, e.g., the actual rotation speed or chamber pressure, may differ from the desired values ​​due to transient effects or system disturbances.

[0017]

[0020] However, if the vibration signal is correlated to a control parameter, such as chamber pressure or rotational speed, the control parameter value determined from the vibration signal can serve as validation or fault detection for another control parameter sensor (e.g., a pressure sensor or motor encoder), or can eliminate the need for other sensors.

[0018]

[0021] Yet another problem in CMP is determining "system health." Malfunctions during polishing (e.g., slipping of the wafer from the carrier head, failure to chuck or dechuck the substrate, stiction between films in the carrier head, etc.) can directly damage the substrate being polished and require extensive downtime for system maintenance. Traditionally, such failures are detected after they occur. For example, visual inspection or a camera may detect that the substrate has slipped out from under the carrier, or a change in the polishing rate may indicate a malfunction.

[0019]

[0022] However, if the vibration signal was correlated to an impending fault condition, it would be possible to diagnose the problem so that corrective action could be taken before a failure occurs.

[0020]

[0023] Yet another problem in CMP is detecting the polishing endpoint. As mentioned above, various techniques have been used to detect the thickness of a layer or to detect the exposure of an underlying layer, such as optical, eddy current, motor current, etc. However, such techniques may require complex sensor systems and some approaches may be unreliable in some applications.

[0021]

[0024] However, if the vibration signal, particularly the distortion on the gimbal in the carrier head, is correlated to a polishing endpoint condition, the polishing endpoint determined from the vibration signal can serve as validation of another monitoring system or can eliminate the need for other monitoring techniques (e.g., eddy current or optical).

[0022]

[0025] The techniques described herein can address any one or more of these issues, either independently or in conjunction.

[0023]

[0026] Generally, one or more of the above problems can be addressed by placing a vibration or displacement sensor on or adjacent to the carrier head and analyzing a signal from the sensor. This approach can also be used for other purposes. For example, the signal can be used to correct errors in one or more polishing parameters. Detecting such errors improves WIW and WTW uniformity.

[0024]

[0027] 1 shows an example of a polishing station of a chemical mechanical polishing system 20. The polishing system 20 includes a rotatable, disk-shaped platen 24 on which a polishing pad 30 is disposed. The platen 24 is operable to rotate about an axis 25. For example, a motor 26 can rotate a drive shaft 28 to rotate the platen 24. The polishing pad 30 can be a two-layer polishing pad having an outer polishing layer 32 and a softer backing layer 34. Grooves 35 can be formed in the polishing surface of the polishing layer 32.

[0025]

[0028] The polishing system 20 may include a supply port or combined supply-rinse arm 36 for dispensing a polishing fluid 38, such as a polishing slurry, onto the polishing pad 30. The polishing system 20 may include a pad conditioner device with a conditioning disk to maintain the surface roughness of the polishing pad 30. The conditioning disk may be positioned at the end of an arm that can swing to sweep the disk radially across the polishing pad 30.

[0026]

[0029] Carrier head 70 is operable to hold substrate 10 against polishing pad 30. Carrier head 70 is suspended from support structure 50, e.g., a carousel or track, and is connected by drive shaft 54 ​​to carrier head rotation motor 56 such that carrier head 70 can rotate about axis 58. Optionally, carrier head 70 may be oscillated laterally by movement along the track, e.g., on a slider on the carousel, or by rotational oscillation of the carousel itself.

[0027]

[0030] Carrier head 70 includes a housing 72 that can be secured to drive shaft 54, a substrate backing assembly 74 including a base 76 and a flexible membrane 78 that define a number of pressurizable chambers 80, a gimbal mechanism 82 (which may be considered part of assembly 74), a loading chamber 84, and a retaining ring 100. The underside of flexible membrane 78 provides a mounting surface for substrate 10.

[0028]

[0031] The housing 72 may be generally circular in shape and may be coupled to the drive shaft 54 ​​for rotation therewith during polishing. There may be a passageway (not shown) extending through the housing 72 for pneumatic control of the carrier head 70. The substrate backing assembly 74 is a vertically movable assembly located below the housing 72.

[0029]

[0032] Assuming the gimbal mechanism 82 is present, the gimbal mechanism prevents lateral movement of the base 76 relative to the housing 72, while allowing the base 76 to be gimbaled (e.g., angularly deflected) relative to the housing 72 and drive shaft 54. For example, if the substrate backing assembly 74 defines a first plane and the housing 72 defines a second plane, the gimbal mechanism 82 facilitates angular deflection between the plane of the housing 72 and the plane of the substrate backing assembly 74 such that they are no longer parallel or coplanar.

[0030]

[0033] The gimbal mechanism can be provided by a bendable flexure or a ball-in-socket type joint. A bendable flexure allows the entire substrate backing assembly 74 to move vertically relative to where the gimbal mechanism 82 contacts the housing 72, while a ball-in-socket type joint holds the substrate backing assembly 74 vertically fixed relative to where the gimbal mechanism 82 contacts the housing 72. In some implementations, the gimbal of the gimbal mechanism is attached to the bottom of a shaft that is itself vertically slidable within a passage in the housing 72. In some implementations, the gimbal mechanism is fixed to the housing and cannot move vertically.

[0031]

[0034] The loading chamber 84 is located between the housing 72 and the base 76. The loading chamber 84 can be pressurized, e.g., to increase the atmospheric pressure within the loading chamber 84 to apply a load, i.e., downward pressure or weight, to the base 76 and thus to the substrate backing assembly 74. The vertical position of the substrate backing assembly 74 relative to the polishing pad 30 can also be controlled by the loading chamber 84. In some embodiments, the substrate backing assembly 74 is not a separate component that can move relative to the housing 72. In this case, the chamber 84 and gimbal 82 are not required.

[0032]

[0035] The polishing system 20 includes at least one in-situ head monitoring system 160. The in-situ head monitoring system 160 includes one or more motion sensors 162 disposed on, i.e., in contact with, or having a field of view of the carrier head 70. In particular, the in-situ head monitoring system 160 can be configured to measure movement of the carrier head and detect vibration emissions caused by various conditions, such as errors in head position, head gimbal, or polishing parameters.

[0033]

[0036] An example of a motion sensor 162 is a direct contact sensor that detects movement of a surface in contact with the motion sensor 162. The direct contact motion sensor 162 is attached to the carrier head 70 with fasteners or adhesive. In particular, one or more of the motion sensors 162 (e.g., motion sensor 162 and motion sensor 162') can be attached to a relatively rigid component of the carrier head, such as a portion of the housing 72 or base 76 ("relatively rigid" as compared to the flexible membrane 78). The motion sensor 162 can be, for example, an accelerometer or a velocity sensor.

[0034]

[0037] 1, the motion sensor 162 is attached to an upper surface of the housing 72 of the carrier head 70. In embodiments using an adhesive layer, the adhesive layer increases the contact area between the motion sensor 162 and the relatively rigid component (e.g., the housing 72) and reduces undesired movement in the motion sensor 162 during the polishing process (e.g., increases the motion coupling between the relatively rigid component and the motion signal sensor 162). However, in some implementations, the motion sensor 162 directly contacts the housing 72 and can be removably secured with mechanical fasteners such as screws or bolts.

[0035]

[0038] Typically, carrier head 70 and platen 24 rotate at speeds ranging from 50 to 150 RPM during the polishing process. Motion sensor 162 monitors high frequency motion, such as vibrations, at frequencies higher than the rotation of carrier head 70. In some examples, the frequency range of vibrations monitored by motion sensor 162 can be in the range of 1 kHz to 100 kHz, e.g., 2 kHz to 40 kHz, or 5 kHz to 80 kHz.

[0036]

[0039] The motion sensor 162 generates an electronic signal indicative of vibrations of the housing 72. The head monitoring system 160 receives the electronic signal from the motion sensor 162 and communicates the electronic signal to a controller 190. The controller 190 processes the received electronic signal to determine one or more carrier head status values ​​for the carrier head 70.

[0037]

[0040] In some implementations, the carrier head monitoring system 160 performs signal processing on the vibration data generated by the motion sensor 162 to filter or denoise the vibration data before communicating the vibration data to the controller 190. In some examples, the head monitoring system 160 applies a smoothing process, a binning process, an averaging process, or a denoising process. In some implementations, the head monitoring system 160 determines a surrogate data parameter, such as the derivative, mean, integral, standard deviation, or variance of the vibration signal. In some implementations, the controller 190 receives the vibration signal from the head monitoring system 160 and performs data processing.

[0038]

[0041] The controller 190 may be configured to generate a value of a carrier head status parameter based on the received electronic signal. More specifically, the electronic signal may be correlated with an actual value of the carrier head status parameter, such as a chamber pressure. For example, increasing the pressure in the chamber may result in a frequency response in the vibration signal. By correlating the frequency response with the chamber pressure, the chamber pressure may be effectively measured. For example, the controller may store a function that depends on the power or intensity in one or more bandwidths in the acoustic frequency spectrum, or a function that depends on the frequency of peaks (including local minima and maxima) in the acoustic frequency spectrum, and output a value of the carrier head status parameter, such as the chamber pressure. As a result, the vibration signal may provide an indirect determination of the chamber pressure without using a direct measurement device, such as using a pressure gauge. The controller 190 may then compare the value to a threshold value to determine an alert. Examples of carrier head status parameters include pressure in one or more pressurizable chambers 80, a gimbaled position of the gimbal mechanism 82, or a gimbaled amount of the carrier head 70.

[0039]

[0042] The controller 190 may be configured to compare the value of the electronic signal to one or more carrier head status thresholds (e.g., thresholds for each carrier head status parameter) to generate an alert in a verification mode or a fault detection mode. The alert may indicate whether the polishing system 20 is functioning properly or improperly, e.g., following programmed guidelines. In such an embodiment, the controller 190 generates an alert in response to the value of the electronic signal exceeding a stored threshold. Examples of alerts may include audio or visual alerts displayed on a user device. Additional or alternative examples of alerts may include notifications sent to networked devices connected to the polishing system 20.

[0040]

[0043] For example, the controller 190 receives an electronic signal including an amplitude value corresponding to the vibration signal. The controller 190 compares the amplitude value to a respective maximum carrier head status threshold. The controller 190 may be configured to determine whether the generated carrier head status value exceeds a threshold status value stored in the controller 190. In this example, if the carrier head 70 is in a fault or failure condition, or may be in an imminent failure condition within a short period of time, the amplitude value of the vibration signal may exceed a corresponding threshold value stored in the controller 190.

[0041]

[0044] The controller 190 can store an array of failure modes that can be correlated with one or more electronic signal values ​​corresponding to portions of the vibration signal. In the previous example, a vibration signal amplitude value that exceeds a corresponding threshold can be associated with a substrate slip failure or a retaining ring failure.

[0042]

[0045] In addition to or in the alternative to failure mode detection, the controller 190 may be configured to modify an operational value of the polishing system 20 in response to the carrier head status value exceeding a corresponding threshold status value. The controller 190 may determine an amplitude of the vibration signal from the electronic signal and compare the amplitude to a carrier head status threshold. An amplitude exceeding a corresponding carrier head status threshold may indicate an improper gimbal amount of the carrier head 70. The controller 190 may modify a gimbal value of the gimbal mechanism 82 in response to the determination.

[0043]

[0046] The motion sensor 162 may be mounted in other locations on the carrier head 70. The motion sensor 162 is mounted (e.g., with a reversible fastener or adhesive) to the side of the carrier head 70 in Figure 2. Mounting the motion sensor 162 on the side increases the distance from the axis 58 of the carrier head 70, thereby increasing sensitivity to movement.

[0044]

[0047] In some cases, a non-contact head monitoring system is desirable. A further example of the motion sensor 162 is an indirect (non-contact) sensor. The motion sensor 162 of FIG. 3 is an optical displacement sensor having a line of sight to the top surface of the carrier head 70. For example, the motion sensor 162 may generate a light beam 164 that reflects from the top surface. The motion sensor 162 receives the reflected light and generates an electronic signal indicative of the vibration signal of the carrier head 70 based on the reflected light. In such an implementation, the optical displacement sensor may have a data frequency rate that is significantly greater than the rotational speed of the carrier head 70, facilitating an increase in the monitoring frequency of the vibration signal. Additionally, such an implementation may have a reduced effect on the dynamics of the carrier head compared to a contact sensor, for example, reducing the possibility of weight imbalance causing undesirable vibrations and failures. Generally, the carrier head 70 is constructed of a highly rigid material (e.g., high stiffness), so that the measurement accuracy of the vibration signal may be within a micron precision range, for example, less than 50 um, less than 10 um, or less than 5 um (e.g., 1 um). In some examples, the light source of the non-contact motion sensor 162 is set independently within the polishing station and reflects off the head.

[0045]

[0048] In some implementations, it is desirable to monitor a motion signal of the gimbal mechanism 82. In Figure 4A, the motion sensor 162 is a strain gauge and is mounted to the gimbal mechanism 82. The strain gauge based motion sensor 162 is an example of a direct contact sensor that monitors the angular deflection or deformation of a mounting surface, such as the gimbal mechanism 82.

[0046]

[0049] A motion sensor 162 is attached to the gimbal mechanism 82 to monitor the most strained area of ​​the gimbal mechanism 82. Such an embodiment improves the precision and accuracy of gimbaling the carrier head 70. Figures 4B and 4C show the gimbal mechanism 82 and the housing 72 in an example where the gimbal mechanism 82 is a flexible gimbal mechanism 82 (Figure 4B) and an example where the gimbal mechanism 82 is a constant height gimbal mechanism 82 (Figure 4C). The lateral shear force exerted on the gimbal mechanism 82 by friction between the substrate 10 and the polishing layer 32 during polishing is indicated by arrow F. The most strained area is approximated by arrow S1 in Figure 4B. The most strained area is approximated by arrow S2 in Figure 4C.

[0047]

[0050] FIG. 5 is a flow chart diagram illustrating a sharpening method 500 for modifying sharpening parameters or generating an alert in response to a detection signal from the head monitoring system 160.

[0048]

[0051] The method includes holding 502 a substrate 10 against polishing layer 32. Substrate 10 is held against polishing layer 32 by a pressurizable chamber 80 of a carrier head 70. Gas pressure within pressurizable chamber 80 is controlled by controller 190 such that substrate 10 is pressed against polishing layer 32. Substrate 10 is held beneath carrier head 70 by a ring assembly 100, which contacts polishing layer 32 during the polishing process.

[0049]

[0052] The method includes generating relative motion between the substrate 10 and the polishing layer 32 (step 504). The polishing apparatus 20 generates at least a portion of the relative motion by actuating the motor 26 to rotate the platen 24 about the axis 25. Rotation of the platen 24 rotates the pad 30, generating relative motion between the substrate 10 and the polishing layer 32. Additionally or alternatively, the polishing system 20 generates a portion of the relative motion by actuating the carrier head rotation motor 56 to rotate the carrier head 70. In some embodiments, the polishing system 20 includes a linear actuator for causing movement of the drive shaft 54 ​​along the support structure 50, which generates a portion of the relative motion between the substrate 10 and the polishing layer 32.

[0050]

[0053] The method includes monitoring the carrier head 70 with an in-situ head monitoring system 160 (step 506). Movement of the platen 24, carrier head 70, and / or substrate 10 causes friction between contacting components that induces a portion of vibration in the housing 72 or gimbal mechanism 82. A motion sensor 162 monitors the movement of one or more of the housing 72, carrier head 70, or gimbal mechanism 82 and receives data corresponding to the movement. The motion sensor 162 can be a contact or non-contact sensor 162, such as any of the examples described herein. The motion data is received by the head monitoring system 160. The head monitoring system 160 generates a vibration signal indicative of the movement. The vibration signal is communicated to the controller 190.

[0051]

[0054] The method includes generating a value of a carrier head status parameter (step 508). The controller 190 receives the vibration signal and determines whether a parameter of the vibration signal exceeds a vibration threshold stored in a storage device (e.g., in the controller 190) of the chemical mechanical polishing system 20. The controller 190 determines that a parameter exceeding an associated threshold corresponds to (e.g., is indicative of) a problem with the polishing process. For example, the problem with the polishing process is an air bubble trapped between the ring assembly 100 or the substrate 10 and the polishing layer 32 of the pad 30. Alternatively or additionally, the problem with the polishing process is a gimbal value, e.g., an angular deflection, of the gimbal mechanism 82.

[0052]

[0055] The controller 190 generates a value of a carrier head status parameter based on the parameter of the vibration signal that exceeds a threshold. The carrier head status parameter can be speed, rotation angle, pressure, gimbaling. The controller 190 compares the determined value with a carrier head status parameter threshold.

[0053]

[0056] The method includes modifying polishing parameters, generating an alert, or both based on the vibration signal (step 510). In response to the determined value exceeding the carrier head status parameter threshold, the controller 190 commands the chemical mechanical polishing system 20 to modify polishing parameters, generate an alert, or both. For example, the controller 190 commands the carrier head 70 to reduce pressure in the loading chamber 84, the pressurizable chamber 80, or both based on the carrier head pressure value exceeding the pressure threshold. In a further example, the controller 190 generates an alert based on a gimbal value exceeding a gimbal threshold, which may include terminating the polishing process.

[0054]

[0057] In some implementations, the controller 190 determines polishing parameters that correspond to the problem of interest. For example, if an air bubble is between the ring assembly 100 and the polishing layer 32, the controller 190 determines that the pressure value of the carrier head 70 against the polishing layer 32 should be reduced sufficiently to allow the air bubble to exit the space between the ring assembly 100 and the polishing layer 32.

[0055]

[0058] For example, if the controller 190 determines that a distortion parameter of the vibration signal exceeds a distortion threshold, the controller 190 determines that an error exists in the gimbal position of the gimbal mechanism 82. In response to determining that one or more errors or parameters exceed a threshold, the controller 190 commands a change in position of the flexible gimbal mechanism 82 by reducing one or more chamber pressures in the pressurizable chamber 80 and reducing the side load on the retaining ring 100 and thus the gimbal mechanism 82. In additional or alternative embodiments, the controller 190 generates an alert based on the determined difference, which may include a visual, audio, textual, or command alert that is communicated to a user device, a network-connected device, or a component of the grinding system 20.

[0056]

[0059] Implementations of the subject matter and functional operations described above may be implemented in digital electronic circuitry, or computer software, firmware, or hardware (including the structures disclosed herein and their structural equivalents), or one or more combinations of these. Implementations of the subject matter described herein, such as storing, maintaining, or displaying artifacts, may be implemented as one or more computer program products (i.e., one or more modules of computer program instructions encoded on a tangible program carrier, such as a computer-readable medium) for execution by or control of the operation of a processing system. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, or one or more combinations thereof.

[0057]

[0060] The term "system" may encompass all apparatus, devices, and machines for processing data, including, for example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, a processing system may include code that creates an execution environment for the computer program (e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of these).

[0058]

[0061] A computer program (also known as a program, software, software application, script, executable logic, or code) can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored as part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., a file that stores one or more modules, subprograms, or portions of code). A computer program can be deployed to run on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communications network.

[0059]

[0062] Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile or volatile memory, media, and memory devices, including, by way of example, semiconductor memory devices (e.g., EPROM, EEPROM, and flash memory devices), magnetic disks (e.g., internal hard disks or removable disks or magnetic tapes), magneto-optical disks, and CD-ROM, DVD-ROM, and Blu-Ray disks. The processor and memory may be supplemented by or incorporated in special purpose logic circuitry. The server may be a general purpose computer, a custom special purpose electronic device, or a combination thereof. An embodiment may include back-end components (such as a data server), or middleware components (such as an application server), or front-end components (such as a client computer with a graphical user interface or web browser) through which a user can interact with an embodiment of the subject matter described herein, or any combination of one or more of such back-end, middleware, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication, such as a communication network. Examples of communication networks include a local area network ("LAN") and a wide area network ("WAN"), such as the Internet.

[0060]

[0063] While this specification contains many details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Certain features described in this specification in the context of separate embodiments may also be combined. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or as part of any suitable combination.

Claims

1. a platen for supporting the polishing pad; a carrier head including a rigid housing configured to hold a surface of the substrate against the polishing pad; a motor for generating relative motion between the platen and the carrier head to polish the substrate; an in situ carrier head monitoring system including a sensor positioned to interact with the housing and to detect vibratory motion of the housing and generate a signal based on the detected vibratory motion; A controller, generating a value for a carrier head status parameter based on signals received from the in situ carrier head monitoring system; modifying polishing parameters or generating an alert based on the carrier head status parameters; a controller configured to A chemical mechanical polishing apparatus comprising:

2. The apparatus of claim 1 , wherein the in situ carrier head monitoring system comprises a sensor mounted on an exterior surface of the housing, and the detected motion is detected vibration.

3. The apparatus of claim 2 , wherein the sensor is mounted on a top surface of the housing.

4. The apparatus of claim 2 , wherein the sensor comprises an accelerometer.

5. The apparatus of claim 1 , wherein the in situ carrier head monitoring system comprises a sensor spaced apart from an exterior surface of the housing and configured to direct electromagnetic energy to the exterior surface of the housing.

6. The apparatus of claim 5 , wherein the sensor comprises a displacement sensor.

7. The apparatus of claim 6 , wherein the displacement sensor is configured to monitor vertical displacement of the housing.

8. The apparatus of claim 6 , wherein the displacement sensor is an optical displacement sensor.

9. The apparatus of claim 8 , wherein the optical displacement sensor is configured to produce measurements at a frequency in the range of 1 kHz to 100 kHz and to determine displacement in the carrier head with a resolution of less than 1 μm.

10. The apparatus of claim 8 , wherein the sensor comprises a laser interferometer.

11. 2. The apparatus of claim 1 , wherein the carrier head comprises a gimbal mechanism, the in situ carrier head monitoring system comprises a strain sensor attached to the gimbal mechanism, and the detected motion is a detected angular deflection of the housing from an axis of rotation of the gimbal mechanism.

12. The apparatus of claim 11 , wherein the gimbal mechanism is a flexible gimbal mechanism or a ball-in-socket gimbal mechanism.

13. The apparatus of claim 1 , wherein the controller is further configured to determine a polishing endpoint based on the carrier head status parameter.

14. The apparatus of claim 1 , wherein the carrier head status parameters include carrier head displacement, shear force, carrier head rotation speed, or carrier head type.

15. The apparatus of claim 1 , wherein the vibrational motion is performed at a frequency above a frequency threshold.

16. holding the substrate against the polishing surface of the polishing pad using a carrier head; generating relative motion between the substrate and the polishing pad; monitoring a vibrational movement of the carrier head with an in situ head monitoring system to generate a signal based on the movement; generating a value for a carrier head status parameter based on the signal from the in situ carrier head monitoring system; modifying polishing parameters or generating an alert based on the determined carrier head status parameters. A polishing method comprising:

17. The method of claim 16 , wherein monitoring the carrier head comprises monitoring an angular deflection of the carrier head relative to an axis of rotation of the carrier head, and the signal is a strain signal.

18. The method of claim 16 , wherein monitoring the carrier head includes monitoring a vertical displacement of the carrier head relative to the in-situ head monitoring system, and the signal is an optical signal.

19. The method of claim 16 , wherein monitoring the carrier head includes monitoring a vibration of the carrier head, and the signal is an acceleration signal.

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