Acoustic monitoring of the carrier head using sensors in the platen

Abstract

The chemical mechanical polishing apparatus comprises a platen for supporting a polishing pad, the platen having a recess; a carrier head for holding the surface of a substrate relative to the polishing pad, the carrier head having a retaining ring for holding the substrate on the underside of the carrier head; a motor for generating relative movement between the platen and the carrier head for polishing the substrate; an insite acoustic monitoring system having an acoustic sensor positioned in the recess for receiving acoustic energy from friction between the substrate and the polishing pad and friction between the retaining ring and the polishing pad; and a controller configured to generate a value for a carrier head status parameter based on an acoustic signal received from the insite acoustic monitoring system, and to change polishing parameters or generate an alert based on the carrier head status parameter.

Description

Technical Field

[0001] The present disclosure relates to chemical mechanical polishing, and more particularly, to the determination of polishing parameters from acoustic signals received during chemical mechanical polishing.

Background Art

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

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

Summary of the Invention

[0004] A chemical mechanical polishing apparatus, including a carrier head for holding a substrate relative to a polishing pad, is disclosed herein. Relative motion is generated between the polishing pad and the carrier head to polish the exposed surface of the substrate. The apparatus includes an acoustic monitoring system that receives acoustic signals from the substrate and the carrier head. The acoustic monitoring system generates corresponding electronic signals that are transmitted to a controller. The controller receives the electronic signals and, based on the electronic signals, generates values ​​for carrier head status parameters. The controller is configured to modify one or more polishing parameters or generate an alert based on the carrier head status parameters.

[0005] In one embodiment, the chemical mechanical polishing apparatus comprises a platen for supporting a polishing pad, the platen having a recess; a carrier head for holding the surface of a substrate relative to the polishing pad, the carrier head having a retaining ring for holding the substrate on the underside of the carrier head; a motor for generating relative movement between the platen and the carrier head for polishing the substrate; an insite acoustic monitoring system having an acoustic sensor positioned in the recess for receiving acoustic energy from friction between the substrate and the polishing pad and friction between the retaining ring and the polishing pad; and a controller configured to generate a value for a carrier head status parameter based on an acoustic signal received from the insite acoustic monitoring system, and to change polishing parameters or generate an alert based on the carrier head status parameter.

[0006] In another embodiment, a polishing method includes: holding a substrate with respect to the polishing surface of a polishing pad using a carrier head; generating relative motion between the substrate and the polishing pad such that an Incitu Acoustic Monitoring System passes below the carrier head; monitoring the carrier head using an Incitu Acoustic Monitoring System positioned below the polishing pad to generate a signal comprising a sequence of segments; identifying a first segment from a sequence of segments corresponding to the sensor being below a first portion of the carrier head; identifying a second segment from a sequence of segments corresponding to the sensor being below a second portion of the carrier head; determining the difference between the first segment and the second segment; and modifying polishing parameters or generating an alert based on the determined difference.

[0007] Details of one or more embodiments are described in the accompanying drawings and the following description. Other features and advantages will become apparent from the description and drawings, as well as from the claims. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic side view of the polishing system, including the Insitu acoustic monitoring system. [Figure 2] This is a schematic top view diagram showing a substrate being polished on a polishing pad, an exemplary path taken by an acoustic sensor during the polishing operation, and an exemplary acoustic signal generated as the sensor moves along the exemplary path. [Figure 3] An illustrative acoustic signal and a diagram showing segments corresponding to different parts of a ring assembly or substrate. [Figure 4] This is a flowchart illustrating an exemplary polishing process. [Figure 5] This is a system diagram of an exemplary computing system. [Modes for carrying out the invention]

[0009] In the diagram, similar reference numerals indicate similar elements.

[0010] One challenge in CMP (Critical Mesh Polishing) is verifying that the polishing system is operating with the desired control parameters, such as the desired rotation speed or chamber pressure. Ideally, this is caused by the controller, which ensures that the appropriate physical components, such as the motor or pressure regulator, operate according to a recipe with the desired control parameter values. However, in practice, the actual values, such as the actual rotation speed or chamber pressure, may differ from the desired values ​​due to transient effects or system failures.

[0011] However, if the acoustic signal correlates with a control parameter, such as chamber pressure or rotation rate, the control parameter value determined from the acoustic signal can be used to verify or detect faults in another control parameter sensor, such as a pressure sensor or motor encoder, thus eliminating the need for other sensors.

[0012] Another challenge in CMP is determining "system health." Failures during polishing, such as wafer displacement from the carrier head, failure to chuck or dechuck the substrate, stiction between films in the carrier head, or unexpected lateral movement of the substrate or carrier head, can cause direct damage to the substrate being polished and may require significant downtime for system maintenance. Traditionally, such failures are only detected after they have occurred. For example, visual inspection or a camera may detect that the substrate has shifted below the carrier, or a change in the polishing rate may indicate a failure.

[0013] However, if the acoustic signal correlates with an impending fault condition, it is possible to diagnose the problem so that corrective measures can be taken before the failure occurs.

[0014] Another problem in CMP is the formation of bubbles between the substrate and the flexible film during chamber pressure ramping. During operation, the pressure in each pressurizable chamber is increased zone by zone according to a policy that can be stored in the controller. If an error occurs in the pressure ramping process, bubbles can be introduced between the substrate and the flexible film. These bubbles alter the pressure profile applied to the substrate and reduce wafer uniformity. There is no real-time technique to identify the pressure ramping process that has produced bubbles between the film and the wafer.

[0015] However, if the acoustic signal correlates with an improper pressure ramp process, it is possible to determine the presence of bubbles or an improper pressure ramp process, thereby allowing corrective measures to be taken before the bubbles affect the polishing of the substrate.

[0016] Another problem in CMP is poor lubrication of the gimbal mechanism. Generally, the gimbal mechanism is lubricated, for example, by oiling, to reduce friction between the moving components when a force is applied to the carrier head that causes gimbaling, for example, when the carrier head rests on a polishing pad of uneven thickness. If a flexible gimbal mechanism is not properly lubricated, the force required to cause gimbaling increases, which can lead to undesirable polishing results, direct damage to the substrate, and increased maintenance of the polishing system.

[0017] However, if the acoustic signal is monitored over time, it is possible to determine if there is a lubrication problem in the gimbal mechanism so that corrective measures can be taken before damage occurs to the gimbal mechanism or before the circuit board is damaged during polishing.

[0018] The polishing process generates acoustic energy when the substrate and the retaining ring of the carrier head interact with the polishing layer of the polishing pad, based at least on frictional contact between two surfaces. This acoustic energy can be received by an acoustic sensor and processed to generate a series of acoustic measurements, in other words, an acoustic signal.

[0019] Segmenting the acoustic signal depending on which surface of the ring assembly or substrate is generating acoustic information facilitates the detection of bubbles or other polishing parameters in erroneous states, such as pressure or gimbaling position. Detecting such errors increases system reliability and reduces system failures and failed polishing operations.

[0020] The techniques described herein can address one or more of these problems, either independently or in combination.

[0021] Figure 1 illustrates an example of a polishing station in a chemical mechanical polishing system 20. The polishing system 20 includes a rotatable disc-shaped platen 24 on which a polishing pad 30 rests. 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 may be a two-layer polishing pad having an outer polishing layer 32 and a softer backing layer 34. The polishing surface of the polishing layer 32 may include, for example, grooves 35 for slurry transport.

[0022] The polishing system 20 may include a supply port or a supply rinse integrated arm 36 for dispensing an abrasive fluid 38, such as an abrasive slurry, onto the polishing pad 30. The polishing system 20 may also include a pad conditioner device 40 having a conditioning disc 42 for maintaining the surface roughness of the polishing pad 30. The conditioning disc 42 may be positioned at the end of an arm 44 that can swing to sweep the disc 42 radially across the polishing pad 30.

[0023] The carrier head 70 is operable to hold the substrate 10 against the polishing pad 30. The carrier head 70 is suspended from a support structure 50, such as a carousel or a track, and is connected by a drive shaft 54 to a carrier head rotation motor 56 so that the carrier head can rotate about the axis 58. Optionally, the carrier head 70 can vibrate laterally, for example, on a slider on a carousel, by movement along a track or by rotational vibration of the carousel itself.

[0024] The carrier head 70 includes a substrate backing assembly 74 that includes a housing 72, a base 76, and a flexible membrane 78 that defines a plurality of pressurizable chambers 80, a gimbal mechanism 82 (which can be regarded as part of the assembly 74), a loading chamber 84, a retaining ring 100, and an actuator 122.

[0025] The housing 72 can generally be circular in shape and is connected to the drive shaft 54 so that it can rotate with the drive shaft 54 during polishing. There may be a passage (not shown) that extends through the housing 72 for pneumatic control of the carrier head 70. The substrate backing assembly 74 is a vertically movable assembly that is located below the housing 72. The gimbal mechanism 82 allows the base 76 to gimbal with respect to the housing 72 while preventing lateral movement of the base 76 with respect to the housing 72. The loading chamber 84 is located between the housing 72 and the base 76 to apply a load, in other words, a downward pressure or weight, to the base 76 and thereby to the substrate backing assembly. The vertical position of the substrate backing assembly 74 with respect to the polishing pad is also controlled by the loading chamber 84. The lower surface of the flexible membrane 78 provides a mounting surface for the substrate 10.

[0026] During the placement of the substrate 10 onto the carrier head 70 or the removal of the substrate 10 from the carrier head 70, the polishing system 20 instructs the carrier head 70 to change the air pressure in the pressurized chambers 80 according to a strategy for chucking (e.g., placing) the substrate 10 onto the carrier head 70 or dechuck (e.g., removing) the substrate 10 from the carrier head 70. Generally, the flexible membrane 78 includes concentric pressurized chambers 80, each of which is individually pressurized. To chuck the substrate 10 onto the carrier head 70, the pressure is increased sequentially from the central chamber outward in a concentric manner to the more distal chambers. To dechuck the substrate 10 from the carrier head 70, the pressure is decreased sequentially in the pressurized chambers 80 from the outermost concentric chambers to the central chamber.

[0027] The continuous pressurization of the chuck process pushes outward any air trapped between the substrate 10 and the pressurizable chamber 80 until the substrate 10 is held in place by the flexible membrane 78 under vacuum. Conversely, the dechuck process continuously decreases the pressure between the pressurizable chamber 80 and the substrate 10 from the outermost chamber inward, so that air enters between the flexible membrane 78 and the substrate 10 until the substrate 10 is no longer held in place by the flexible membrane 78 under vacuum.

[0028] The polishing system 20 includes at least one insite acoustic monitoring system 160. The insite acoustic monitoring system 160 includes one or more acoustic sensors 162 positioned on the underside of the surface of the substrate 10, closer to the polishing pad 30. Each acoustic sensor may be installed at a location on the platen 24. In particular, the insite acoustic monitoring system may be configured to sense acoustic energy, for example, acoustic emission caused by stress in the polishing pad, substrate, or retaining ring. Generally, this acoustic energy is in the form of compression waves transmitted through the material (as opposed to bulk motion).

[0029] The acoustic sensor 162 is positioned in a recess 164 in the platen 24 and positioned to receive acoustic energy through the polishing pad 30, for example, through an acoustic window 118 in the polishing pad 30. The acoustic sensor 162 may be connected to a power supply and / or other signal processing electronics 166 by a circuit configuration 168 through a rotating coupling, for example, a mercury slip ring. The signal processing electronics 166 may be connected to a controller 190.

[0030] The insite acoustic monitoring system 160 may be 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 to 400 kHz or 200 kHz to 1 MHz. For example, a frequency range of 225 kHz to 350 kHz may be monitored for monitoring the polishing of interlayer dielectric (ILD) in shallow trench isolation (STI). As another example, the passive mode frequency may range from 500 kHz to 900 kHz.

[0031] The portion of the backing layer 34 directly above the acoustic sensor 162 may include an acoustic window 118. The acoustic window 118 has a lower acoustic attenuation coefficient than the surrounding backing layer 34. The material of the acoustic window 118 has a sufficiently low acoustic attenuation coefficient, for example, to provide a satisfactory signal for acoustic monitoring. Generally, the acoustic attenuation coefficient should be as low as possible (in other words, no absorption), for example, less than 2, to provide a satisfactory signal for acoustic monitoring.

[0032] In some implementations, the acoustic window 118 is formed from a different material than the backing layer 34. This allows the backing layer 34 to be composed of a wider range of materials to meet the needs of CMP operation. The acoustic window 118 may be composed of a non-porous material, such as a solid. For example, the acoustic material may be a polymer, such as polyurethane.

[0033] The acoustic window 118 may be wider than the acoustic sensor 162, for example, as shown in Figure 1, or the acoustic window 118 and the acoustic sensor 162 may be substantially equal in width (for example, within 10%). If the acoustic window 118 is narrower than the acoustic sensor 162, the sensor may also contact the bottom of the backing layer 34.

[0034] The acoustic sensor 162 is a contact acoustic sensor 162 having a surface connected to (for example, in direct contact with) a portion of the backing layer 34 and / or the acoustic window 118, or in contact only through the adhesive layer. For example, the acoustic sensor 162 may be an electromagnetic acoustic transducer or a piezoelectric acoustic transducer. The piezoelectric sensor may include a rigid contact plate, such as stainless steel, positioned to contact the object to be monitored, and a piezoelectric assembly on the back of the contact plate, such as a piezoelectric layer sandwiched between two electrodes.

[0035] The acoustic sensor 162 may be fixed to a portion of the backing layer 34 and / or to the acoustic window 118 by an adhesive layer. The adhesive layer can increase the contact area between the acoustic sensor 162 and the backing layer 34 and / or the acoustic window 118, reduce undesirable movement of the acoustic sensor 162 during polishing operations, and reduce the presence of gas pockets between the acoustic sensor 162 and the backing layer 34. However, in some implementations, the acoustic sensor 162 is in direct contact with the acoustic window 118.

[0036] The acoustic window 118 extends through the backing layer 34 such that one surface, for example, the upper surface, is in contact with the lower surface of the polishing layer 32. The opposing surface, for example, the bottom surface, may be coplanar with the lower surface of the backing layer 34.

[0037] The acoustic window 118 may be composed of a non-porous material. Generally, non-porous materials transmit acoustic energy with reduced noise and dispersion compared to porous materials. The material of the acoustic window 118 may have a compressibility within the range of the compressibility of the surrounding matrix material 204, which reduces the effect of the acoustic window 118 on the polishing characteristics of the polishing layer 32. The acoustic window 118 may be composed of one or more of polyurethane, polyacrylate, polyethylene, or other polymers having a sufficiently low acoustic impedance coefficient. The acoustic window 118 is shown extending through the entire thickness of the backing layer 34. The acoustic sensor 162 extends through an opening in the platen 24 and contacts the underside of the window 118.

[0038] In some implementations, as shown in Figure 1, the acoustic window 118 extends through the thickness of the pad 30. As shown in Figure 1, the acoustic window 118 extends through both the polishing layer 32 and the backing layer 34. Here, the acoustic window 118 has a lower acoustic impedance than the surrounding polishing layer 32 and backing layer 34. The acoustic window 118 is positioned such that its upper surface is coplanar with the polishing surface 112a, and its bottom surface is coplanar with the lower surface of the backing layer 34 that contacts the platen 24, for example, the bottom surface 114b. The acoustic sensor 162 contacts the exposed surface of the acoustic window 118 and receives the transmitted acoustic energy.

[0039] The acoustic window 118 is formed from a different material than the polishing layer 32. This allows the polishing layer 32 to be composed of a wider range of materials to meet the needs of CMP operation. In some implementations, the acoustic transmittance of both the polishing layer 32 and the backing layer 34 is sufficiently high, and the acoustic window is not required. In this case, the acoustic sensor 162 may be placed in direct contact with the underside of the backing layer 34.

[0040] Referring now to Figure 2, an overhead view of the platen 24 and the supported polishing pad 30 is shown, along with the substrate 10 enclosed by the retaining ring 100. During the polishing operation, the relative movement between the pad 30 and the substrate 10 is generated by the rotation of the platen 24, the rotation or linear motion of the carrier head 70 pressing on the substrate 10, or a combination thereof. A sensor 162 (and a window 118, if present) is shown, and as the platen 24 and the supported pad 30 rotate in direction 124, the sensor 162 follows a path 102 with respect to the reference frame of Figure 2. As the sensor 162 follows the path 102 during the polishing operation, the sensor 162 moves below the ring assembly 100 and separate parts of the substrate 10, for example, when the path 102 intersects with a portion of the substrate 10 or a portion of the retaining ring 100.

[0041] The acoustic sensor 162 is in contact with the window 118 and generates acoustic data during the polishing operation. The acoustic sensor 162 generates a series of acoustic measurements as the sensor moves along the path 102. This series of measurements includes measurements when the sensor 162 (or window 118) is not below or in contact with the retaining ring 100 or the substrate 10. Data generated before the sensor 162 passes below the retaining ring 100, for example, before and when it enters path section 106, is called "leading off-wafer data". An exemplary path section from which leading off-wafer data is collected is shown as path section 110.

[0042] As sensor 162 passes beneath the carrier head 70, retaining ring 100, or substrate 10, the acoustic sensor 162 measures the acoustic energy generated by the contact between the carrier head 70, retaining ring 100, or substrate 10 and the polishing pad 30 and window 118. Path portions 104 and 108 correspond to sensor 162 being beneath two portions of the retaining ring 100, and path portion 106 corresponds to sensor 162 being beneath the substrate 10. Data generated when sensor 162 is beneath the substrate 10, for example, in path portion 106, is called "on-wafer data." Due to attenuation of acoustic energy as it travels through the polishing pad 30 and window 118, the acoustic energy reaching sensor 162 is primarily caused by friction between the polishing pad 30 (including window 118) and certain components directly above sensor 162, such as the retaining ring 100 or substrate 10. Information about the components can be obtained by analyzing the path portions of the signals corresponding to the components.

[0043] Data generated after the sensor 162 has passed under the second portion of the holding ring 100, for example, after exiting path portion 108, is called "trailing off-wafer data." An exemplary path portion from which trailing off-wafer data is collected is shown as path portion 112.

[0044] The controller 190 of the acoustic monitoring system 160 receives acoustic data from the acoustic sensor 162. In some implementations, the controller displays the measured acoustic signal on a display, such as a computer monitor.

[0045] Referring next to Figures 2 and 3, an exemplary acoustic signal 300 is shown. The acoustic monitoring system 160 processes the acoustic signal 300 and subdivides it into segments corresponding to the position of the sensor 162 below the carrier head 70, for example, below the ring assembly 100 or the substrate 10. The acoustic monitoring system 160 subdivides the acoustic signal 300 into segments according to the measurement position determined from the angular position of the platen, in other words, the position of the sensor. In some implementations, different segments of the signal may be distinguished based on the average amplitude of the acoustic signal 300. The sequence of segments is a time-dependent sequence corresponding to the acoustic data continuously generated by the acoustic sensor 162 over a period of time.

[0046] In some implementations, the acoustic monitoring system 160 performs signal processing on the acoustic data generated by the acoustic sensor 162, such as filtering the acoustic data to remove noise, before communicating the acoustic data to the controller 190. The filtering may be a low-pass filter or a running window average to smooth the measurement signal from the sensor 162. In some examples, the acoustic monitoring system 160 generates an average value for the measurement signal within each segment.

[0047] In the example in Figure 3, the acoustic signal 300 includes an off-wafer segment 322 corresponding to “leading off-wafer data”, segments 324 and 332 corresponding to the window 118 being below the retaining ring 100, for example, data collected on path portions 104 and 108, segment 326 corresponding to the window 118 being below the carrier head 70 and not in contact with the ring assembly 100 or the substrate 10, and an on-wafer segment 328 corresponding to the window 118 being below the substrate 10, for example, “on-wafer data”, and an off-wafer segment 334 corresponding to “trailing off-wafer data”. During the polishing operation, friction presses the substrate 10 against the trailing inner surface of the retaining ring 100, and therefore the on-wafer segment 328 is adjacent to the carrier head section 332 in the acoustic signal 300. In some examples, segment 326 may not appear in the acoustic signal 300 received by the acoustic monitoring system 160. Generally, the gap between the leading substrate 10 and the ring assembly 100 of the path 102 can be 2mm to 3mm, which is smaller than the sensor 162 and therefore may be virtually undetectable, for example, indistinguishable from the rest of the acoustic signal 300.

[0048] The acoustic monitoring system 160 communicates the acoustic signal 300 to the controller 190. The controller 190 processes the received acoustic signal 300 to compare the values ​​of the characteristics of the signal 300 with predetermined thresholds or to determine changes in the characteristics of the signal 300. 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 in the frequency spectrum of the segment of the signal, the total power in a certain bandwidth range of the frequency spectrum of the segment of the signal, the frequency-weighted average power, or the location (frequency) of peaks or troughs in the frequency spectrum of the segment of the signal. In some implementations, the controller 190 determines alternative data parameters of the acoustic signal 300, or more specifically, one or more segments of the acoustic signal 300, such as derivatives, mean, frequency-weighted average power, integral, standard deviation, or variance.

[0049] For example, the controller 190 determines differences in values ​​for the characteristics of one or more segments of the acoustic signal 300, such as differences between on-wafer segment 328 and off-wafer segments 322 and / or 334, differences between leading carrier head segment 324 and trailing carrier head segment 332, or differences between on-wafer segment 328 and carrier head segments 324 and / or 332. The controller 190 may also determine differences in values ​​for the characteristics of the acoustic signal 300 over time, such as differences between consecutive rotations of the platen, differences between two or more substrates 10, or differences in the acoustic signal 300 over the operating time period of the polishing system 20 (e.g., weeks or months).

[0050] In some implementations, the controller 190 compares the characteristics of the acoustic signal 300 with one or more thresholds. For example, the controller 190 compares the maximum value (e.g., maximum amplitude) of one or more segments of the acoustic signal 300 with their respective maximum thresholds.

[0051] In general, the acoustic monitoring system 160 determines the presence of defects, inaccurate or undesirable polishing parameters, or a combination thereof, from the acoustic signal 300 by comparing one or more segments of the acoustic signal 300 with another segment, by comparing the acoustic signal 300 with hysteretic acoustic signals generated on different substrates, or both. If the difference between the values ​​for the characteristics of two segments of the acoustic signal exceeds a threshold, one of the problems may be indicated. If the on-wafer signal power is significantly lower than expected, or if there is a significant drop in signal power in the relevant region of the signal that is not related to an equivalent reduction in the expected pressure applied to the wafer, bubbles may be present. If the difference between the leading and trailing edge ring signal powers (324 and 332) is outside the characterized tolerance range, the gimbal position may be misaligned.

[0052] The controller 190 generates values ​​for carrier head status parameters based on one or more segments of the received acoustic signal 300. Examples of carrier head status parameters include the pressure in one or more pressurizable chambers 80, or the gimbal position of the gimbal mechanism 82 (e.g., height or angular displacement). The controller 190 compares the carrier head status value with a threshold status value stored in the controller 190. In response to the carrier head status value exceeding the corresponding threshold status value, the controller 190 can generate an alert or change the operating value of the polishing system 20.

[0053] In this example, the controller 190 determines the difference in average amplitude between the leading carrier head segment 324 and the trailing carrier head segment 332. Such an amplitude difference may indicate an inappropriate pressure in one or more chambers 80 that could cause improper gimbaring of the carrier head 70. The controller 190 can generate an alert in response to the determination.

[0054] The controller 190 can determine the difference in average amplitude between the leading carrier head segment 324 and the trailing carrier head segment 332 over multiple substrate polishing operations 10. A determination that the amplitude difference exceeds a threshold, or that the average amplitude is fluctuating, may indicate poor lubrication of the gimbal mechanism 82. In response to a determination that indicates the gimbal mechanism 82 requires maintenance, the controller 190 generates an alert.

[0055] In another example, the controller 190 determines the variation in segment 326, or on-wafer segment 328. The variation can be calculated as the standard deviation of the signal across each segment, or as the difference between the maximum and minimum values ​​across each segment. The variation can be compared to a stored variation threshold. In some examples, high variation in on-wafer segment 328, in other words, variation exceeding the threshold, may indicate the presence of bubbles between the substrate 10 and the polishing layer 32. Bubbles reduce polishing effectiveness by reducing the contact area between the substrate 10 and the polishing layer 32. Detecting bubbles facilitates the adjustment of one or more polishing parameters to remove the bubbles, which improves on-wafer polishing. In response to the determination of the presence of bubbles, the controller 190 can generate an alert, terminate the polishing process, or both.

[0056] In some implementations, the controller 190 generates an alert in response to the received acoustic signal 300, for example, in response to one or more segments 322-334 in the signal 300. Examples of alerts may include audio alerts 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.

[0057] Figure 4 is a flowchart illustrating a polishing method 400 for changing polishing parameters or generating an alert in response to detected differences in segments of the acoustic signal 300.

[0058] The substrate 10 is held against the polishing layer 32 of the polishing pad 30, which is supported by the platen 24, and is pressed, for example, by the pressurizable chamber 80 of the carrier head 70 (step 402). The substrate 10 is held below the carrier head 70 by a retaining ring 100 that contacts the polishing layer 32 during the polishing operation.

[0059] Relative motion is generated between the substrate 10 and the polishing layer 32 (step 404). For example, the polishing system 20 can generate at least a portion of the relative motion by operating a motor 26 to cause the platen 24 to rotate about an axis 25. Additional or alternative, the polishing system 20 can generate a portion of the relative motion by operating a carrier head rotating motor 56 to cause the carrier head 70 to rotate. In some implementations, the polishing system 20 includes a linear actuator to cause the movement of a drive shaft 54 ​​along a support structure 50, which generates a portion of the relative motion between the substrate 10 and the polishing layer 32. Polishing fluid 38 is added to the polishing layer 32 from a supply rinse arm 36 to improve the polishing of the surface of the substrate 10 that is in contact with the polishing layer 32.

[0060] The in-situ acoustic monitoring system 160 monitors the carrier head 70 during the polishing operation (step 406). The acoustic monitoring system 160 includes an acoustic sensor 162 located within the platen 24, for example, in a recess 164 of the platen 24. The acoustic sensor 162 contacts a portion of the polishing pad 30, such as the surface of the backing layer 34. In some implementations, the acoustic sensor 162 contacts the surface of the polishing layer 32. As an addition or alternative, the polishing layer 32 and / or the backing layer 34 include an acoustic window 118 into which the acoustic sensor 162 contacts.

[0061] As the acoustic sensor 162 sweeps below the carrier head 70 along the path 102, the acoustic sensor 162 receives acoustic energy corresponding to the contact between the retaining ring 100 or the substrate 10 and the polishing layer 32. The acoustic energy is received by the acoustic monitoring system 160, which generates an acoustic signal 300 that is communicated to the controller 190.

[0062] The controller 190 receives the acoustic signal 300 and generates a value for the carrier head status parameter based on the received acoustic signal 300 (step 408). The controller 190 can generate a value for the carrier head status parameter by dividing the received acoustic signal 300 into a sequence of segments and determining the differences between the segments. Alternatively or additionally, the controller 190 can generate a value for the carrier head status parameter by determining the differences between different acoustic signals 300 received from different boards 10. Generating the value may include the following steps 410-414.

[0063] The acoustic signal 300 is divided into segments, for example, a sequence of segments 322-334, by the controller 190 or the acoustic monitoring system 160. Determining the differences between segments includes the controller 190 identifying a first segment from the sequence of segments 322-334 that corresponds to the sensor 162 being located below the carrier head 70 or a portion of the substrate 10 (step 410). Segments 322-334 have acoustic parameter values, such as amplitude values ​​or fluctuation values. The amplitude / fluctuation values ​​for each of segments 322-334 are compared to their respective threshold values ​​for the acoustic signal received from the carrier head 70, the ring assembly 100, or the substrate 10.

[0064] The controller 190 identifies a second segment from the sequence of segments 322-334 that corresponds to the acoustic sensor 162 being located below the second portion of the carrier head 70 (step 412). The second segment corresponds to a different segment from the first segment.

[0065] The controller 190 determines the difference between the selected segments (step 414). The controller 190 compares the first and second selected segments and determines the difference. In some examples, the difference determined by the controller 190 includes subtraction, weighted averaging, or performing a mathematical process on the segments and determining the difference between the results of the mathematical process.

[0066] The controller 190 modifies the polishing parameters, generates an alert, or both based on the determined difference (step 416). The controller 190 determines the difference between the selected segments and determines which problem in the polishing process is related to the difference. Each problem may be related to a different difference, and the associations may be stored in the controller 190. For example, a problem in the polishing process may be bubbles trapped between the ring assembly 100 or the substrate 10 and the polishing layer 32 of the pad 30. In one example, bubbles trapped between the substrate 10 and the carrier head 70 may result in a difference between the on-wafer segment 328 and a historical on-wafer segment stored in the controller 190 from a previous polishing operation. As an alternative or additional example, a problem in the polishing process may be gimbering of the gimbal mechanism 82. A gimbering problem may result in a difference between the mean and / or maximum values ​​of the leading carrier head section 324 and the trailing carrier head section 332.

[0067] In some implementations, the controller 190 determines polishing parameters corresponding to the relevant problem. For example, in a case where bubbles are between the ring assembly 100 and the polishing layer 32, the controller 190 determines that the pressure value of the carrier head 70 on the polishing layer 32 should be reduced sufficiently for the bubbles to exit the space between the ring assembly 100 and the polishing layer 32.

[0068] In some examples, the controller 190 determines the difference between the leading carrier head segment 324 and the trailing carrier head segment 332. For example, if the controller 190 determines the difference in amplitude between the leading carrier head segment 324 and the trailing carrier head segment 332, the controller 190 determines that there is an error in the gimbal position of the gimbal mechanism 82. In one example, the controller 190 changes the height of the assembly 74 by increasing the pressure in the chamber 84. In another example, the controller 190 indirectly changes the angular orientation of the assembly 74 relative to the housing 72 by increasing the gas pressure in one or more of the pressurizable chambers 80.

[0069] In an additional or alternative example, the controller 190 may generate an alert based on the determined difference, and the alert may include a visual, audio, text, or command alert that is communicated to a user device, a networked device, or a component of the polishing system 20.

[0070] Figure 5 is a block diagram of an exemplary computer system 500. The system 500 includes a processor 510, memory 520, a storage device 530, and one or more input / output interface devices 540. Each of the components 510, 520, 530, and 540 may be interconnected, for example, using a system bus 550.

[0071] The processor 510 is capable of processing instructions for execution within the system 500. The term “execution” as used herein refers to the technique by which program code causes the processor to execute one or more processor instructions. In some implementations, the processor 510 is a single-threaded processor. In some implementations, the processor 510 is a multi-threaded processor. The processor 510 is capable of processing instructions stored in memory 520 or in the storage device 530. The processor 510 may perform operations such as monitoring the polishing process using the acoustic monitoring system described herein.

[0072] Memory 520 stores information within the system 500. In some implementations, memory 520 is a computer-readable medium. In some implementations, memory 520 is a volatile memory unit. In some implementations, memory 520 is a non-volatile memory unit.

[0073] The storage device 530 can provide high-capacity storage to the system 500. In some implementations, the storage device 530 is a non-transient computer-readable medium. In various different implementations, the storage device 530 can include, for example, a hard disk device, an optical disk device, a solid-state drive, a flash drive, a magnetic tape, or some other high-capacity storage device. In some implementations, the storage device 530 may be a cloud storage device, for example, a logical storage device that includes one or more physical storage devices distributed over a network and accessed using the network.

[0074] The input / output interface device 540 provides input / output operations to the system 500. In some implementations, the input / output interface device 540 may include one or more network interface devices, such as an Ethernet interface; serial communication devices, such as an RS-232 interface; and / or wireless interface devices, such as an 802.11 interface, a 3G wireless modem, or a 4G wireless modem. The network interface device enables the system 500 to communicate, for example, send and receive data. In some implementations, the input / output device may include a driver device configured to receive input data and send output data to other input / output devices, such as a keyboard, printer, and display device. In some implementations, mobile computing devices, mobile communication devices, and other devices may be used.

[0075] The software, when executed, may be implemented by instructions that cause one or more processing devices to perform the processes and functions described above, for example, monitoring the polishing process using the acoustic monitoring system described herein. Such instructions may include, for example, interpreter-type instructions such as script instructions, or executable code, or other instructions stored on a computer-readable medium.

[0076] In some examples, the system 500 is contained within a single integrated circuit package. This type of system 500, in which both the processor 510 and one or more other components are contained within a single integrated circuit package and / or manufactured as a single integrated circuit, is sometimes referred to as a microcontroller. In some implementations, the integrated circuit package includes pins corresponding to input / output ports that can be used, for example, to communicate signals with one or more input / output interface devices 540.

[0077] An exemplary processing system is illustrated in Figure 5, but the implementations of the subject matter and functional operation described above may be implemented in other types of digital electronic circuit configurations, or in computer software, firmware, or hardware, or one or more combinations thereof, including the structures disclosed herein and their structural equivalents. Implementations of the subject matter described herein, such as storing, maintaining, and displaying artifacts, may be implemented as one or more computer program products for execution by the processing system or for controlling the operation of the processing system, in other words, as tangible program carriers, for example, one or more modules of computer program instructions encoded on a computer-readable medium. 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.

[0078] The term "system" may encompass all devices, equipment, 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 the execution environment for the computer program in question, such as processor firmware, a protocol stack, a database management system, an operating system, or code that constitutes one or more of these.

[0079] Computer programs (also known as programs, software, software applications, scripts, 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 standalone programs or as modules, components, subroutines, or other units suitable for use in a computing environment. Computer programs do not necessarily correspond to files in a file system. A program may be stored in 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, or in a group of coordinated files (e.g., a file that stores one or more modules, subprograms, or parts of code). Computer programs can be deployed to run on one computer, or on multiple computers located in one site, or distributed across multiple sites and interconnected by a communication network.

[0080] Computer-readable media suitable for storing computer program instructions and data include, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks or removable disks or magnetic tapes; magneto-optical disks; and all forms of non-volatile or volatile memory, media, and memory devices, including CD-ROMs, DVD-ROMs, and Blu-ray discs. Processors and memory may be supplemented by or incorporated into dedicated logic circuit configurations. A server may be a general-purpose computer, a custom-made dedicated electronic device, or a combination of these.

[0081] Although this specification contains many details, these should not be interpreted as limitations on the scope of what can be claimed, but rather as descriptions of features specific to particular examples. Some features described herein in relation to separate implementations may be combined. Conversely, various features described in relation to a single implementation may be implemented separately or in any preferred partial combination in multiple embodiments.

Claims

1. A platen for supporting a polishing pad, wherein the platen has a recess, A carrier head for holding the surface of a substrate with respect to the polishing pad, wherein the carrier head is provided with a retaining ring on the lower side of the carrier head for holding the substrate, A motor for generating relative motion between the platen and the carrier head in order to polish the substrate, An acoustic monitoring system comprising an acoustic sensor disposed in the recess that receives acoustic energy from friction between the substrate and the polishing pad, and from friction between the retaining ring and the polishing pad, It is a controller, Based on the acoustic signal received from the aforementioned insitu acoustic monitoring system, a value for the carrier head status parameter is generated. Based on the aforementioned carrier head status parameters, the polishing parameters are modified or an alert is generated. A controller configured to perform the following actions A chemical mechanical polishing apparatus equipped with the following features.

2. The apparatus according to claim 1, wherein the polishing parameters include one or more of the following: the amount of gimbaring of the carrier head, whether the chamber in the carrier head is properly pressurized, the presence of air bubbles between the substrate and the carrier head, or whether the substrate is chucked to the carrier head.

3. The apparatus according to claim 1, wherein the acoustic sensor is attached to the bottom surface of the polishing pad.

4. The apparatus according to claim 1, wherein the polishing pad includes an acoustic window, and the acoustic sensor is in contact with the bottom surface of the acoustic window.

5. The apparatus according to claim 1, wherein the controller is further configured to determine the difference between at least two different portions of the acoustic signal.

6. The apparatus according to claim 5, wherein the controller is further configured to generate an alert based on the difference exceeding a threshold.

7. The apparatus according to claim 6, wherein the controller is further configured to determine the difference between the acoustic signal and a hierarchical acoustic signal from a previous substrate, wherein the hierarchical acoustic signal is stored in the controller.

8. The apparatus according to claim 1, wherein the controller is further configured to determine the difference between the acoustic signals from a first portion and a second portion of the surface of the ring assembly.

9. The carrier head is used to hold the substrate against the polishing surface of the polishing pad, The insitu acoustic monitoring system generates relative motion between the substrate and the polishing pad so that it passes below the carrier head, In order to generate a signal comprising a sequence of segments, the carrier head is monitored using an insitu acoustic monitoring system located below the polishing pad, Identifying a first segment corresponding to the sensor being located below the first portion of the carrier head from the sequence of segments, Identifying a second segment corresponding to the sensor being located below the second portion of the carrier head from the sequence of segments, To determine the difference between the first segment and the second segment, Based on the determined difference, the polishing parameters may be changed or an alert may be generated. A polishing method that includes [a specific feature / feature].

10. The method according to claim 9, wherein the first and second portions of the carrier head are the first and second portions of the ring assembly of the carrier head.

11. The method according to claim 9, wherein the polishing parameter is the pressure of the carrier head.

12. The method according to claim 9, further comprising detecting, based on the signal, that the substrate has left the polishing surface of the polishing pad.

13. The method according to claim 9, further comprising detecting the presence of bubbles based on the aforementioned signal.

14. One or more computers, The carrier head is used to hold the substrate against the polishing surface of the polishing pad, The in-situ monitoring system generates relative motion between the substrate and the polishing pad so that it passes below the carrier head, In order to generate a signal comprising a sequence of segments, the carrier head is monitored using an insitu acoustic monitoring system located below the polishing pad, Identifying a first segment corresponding to the sensor being located below the first portion of the carrier head from the sequence of segments, Identifying a second segment corresponding to the sensor being located below the second portion of the carrier head from the sequence of segments, To determine the difference between the first segment and the second segment, Based on the determined difference, the polishing parameters may be changed or an alert may be generated. A computer program product comprising a non-temporary computer-readable medium containing instructions for executing a computer program.

15. The computer program product according to claim 14, wherein the first and second portions of the carrier head are the first and second portions of the retaining ring of the carrier head.

16. The computer program product according to claim 14, wherein the polishing parameter is the pressure of the carrier head.

17. The computer program product according to claim 14, further comprising detecting, based on the signal, that the substrate has left the polishing surface of the polishing pad.

18. The computer program product according to claim 14, further comprising detecting the presence of bubbles based on the aforementioned signal.

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