Chemical mechanical polishing vibration measurement using optical sensor

Abstract

A chemical mechanical polishing apparatus includes a platen to support a polishing pad, a carrier head to hold a substrate against a polishing surface of the polishing pad, a motor to generate relative motion between the platen and the carrier head to polish an overburden layer on the substrate, an in-situ pad vibration monitoring system including a light source to emit a light beam and a sensor to receive reflections of the light beam from a reflective surface of the polishing pad, and a controller configured to detect exposure of an underlying layer due to polishing of the substrate based on measurements from the sensor of the in-situ pad vibration monitoring system.

Description

Technical Field

[0001] This specification relates to chemical mechanical polishing, and more specifically to measuring the vibration of a chemical mechanical polishing pad to detect layer transitions. Background Technology

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconducting, or insulating layers on a silicon wafer. One manufacturing step involves depositing a filler layer on a non-planar surface and planarizing the filler layer. For some applications, the filler layer is planarized until the top surface of a patterned layer is exposed. For example, a conductive filler layer may be deposited on a patterned insulating layer to fill trenches or holes in the insulating layer. After planarization, portions of the remaining metal layer between the raised patterns of the insulating layer form vias, plugs, and lines that provide conductive paths between thin-film circuits on the substrate. For other applications, such as oxidation polishing, the filler is planarized until a predetermined thickness is left on the non-planar surface. Furthermore, planarization of the substrate surface is often required for photolithography.

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

[0004] One challenge in CMP is determining whether the polishing process is complete—for example, whether the substrate layer has been planarized to the desired flatness or thickness, or when the required amount of material has been removed. Variations in slurry distribution, polishing pad conditions, the relative speed between the polishing pad and the substrate, and the load on the substrate can cause variations in the material removal rate. These variations, along with variations in the initial thickness of the substrate layer, lead to variations in the time required to reach the polishing endpoint. Therefore, the polishing endpoint cannot typically be determined solely as a function of polishing time.

[0005] In some systems, the substrate is monitored in situ during polishing, for example, by monitoring the torque required by a motor-driven rotating platform or carrier head. However, existing monitoring technologies may not meet the increasing demands of semiconductor device manufacturers. Summary of the Invention

[0006] In one aspect, a chemical mechanical polishing apparatus includes: a platform for supporting a polishing pad; a support head for holding a substrate against the polishing surface of the polishing pad; a motor for generating relative motion between the platform and the support head to polish an overlay on the substrate; an in-situ pad vibration monitoring system including a light source for emitting a light beam and a sensor for receiving reflections of the light beam from a reflective surface of the polishing pad; and a controller configured to detect exposure of the underlying layer attributable to substrate polishing based on measurements from the sensors of the in-situ pad vibration monitoring system.

[0007] The advantages of implementation may include, but are not limited to, one or more of the following.

[0008] This document discloses an apparatus and method for using an in-situ displacement monitoring system, which includes a light source and a sensor for detecting vibrations in a polishing pad of a chemical mechanical polishing (CMP) apparatus. The detected vibrations correspond to vibrations caused by friction (e.g., released stress energy) between a substrate moving on a grooved surface of the polishing pad and the slurry. Frequency domain analysis of the vibrations is performed based on the detected vibrations, and this frequency domain analysis is monitored to determine polishing endpoints, such as detecting the exposure of the substrate.

[0009] Monitoring displacement at high sampling rates provides a wide spectral resolution in vibration profiles. For example, monitoring displacement up to 350 kHz provides vibration profile resolution ranging from less than 1 Hz to 175 kHz. Real-time frequency domain analysis enables precise and accurate detection of vibration profile changes corresponding to the exposed subsurface.

[0010] It can achieve one or more of the following potential advantages: It allows for more reliable detection of underlying material exposure; it allows for more reliable stopping of polishing; and it can improve inter-wafer uniformity.

[0011] Details of one or more embodiments are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will be apparent from the implementation, the drawings, and the claims. Attached Figure Description

[0012] Figure 1 The illustration shows a schematic cross-sectional view of an example of a polishing device.

[0013] Figure 2A The illustration shows a schematic cross-sectional view of a vibration monitoring sensor for an insert in a polishing pad.

[0014] Figure 2B The illustration shows a schematic cross-sectional view of another implementation of a vibration monitoring sensor for monitoring an insert passing through a polishing pad.

[0015] Figure 2C The illustration shows a schematic cross-sectional view of another implementation of a vibration monitoring sensor in a portion of a bonding polishing pad.

[0016] Figure 3 The illustration shows a schematic top view of a platform equipped with acoustic monitoring sensors.

[0017] Figure 4 The flowchart illustrates the acoustic monitoring method.

[0018] The same reference numerals and symbols indicate the same elements in each figure. Detailed Implementation

[0019] In some semiconductor wafer processes, topcoats (e.g., metal, silicon oxide, or polysilicon) are polished until an underlying layer (e.g., a dielectric layer) is exposed, such as silicon oxide, silicon nitride, or a high-dielectric-constant dielectric layer. During the polishing of the topcoat, friction between the slurry, the substrate, and the polishing pad generates vibrations. For some applications, the vibration spectrum changes when the underlying layer is exposed. The polishing transition point can be determined by detecting this vibration change. For example, an acoustic sensor can be mechanically coupled to the polishing pad. However, such monitoring techniques may not meet the increasing demands of semiconductor device manufacturers. Specifically, consistent low-loss acoustic coupling between the polishing pad and the acoustic sensor can be difficult or expensive.

[0020] By generating a light beam and measuring the reflection of the beam from the polishing pad, it is possible to measure the vibration of the polishing pad with less attenuation and thus with reduced noise.

[0021] Figure 1 An example of a polishing apparatus 100 is illustrated. The polishing apparatus 100 includes a rotatable disc-shaped platform 120 on which a polishing pad 110 is located. The platform is operable to rotate about an axis 125. For example, a motor 121 (e.g., a DC induction motor) can rotate a drive shaft 124 to rotate the platform 120.

[0022] The polishing pad 110 may be a two-layer polishing pad, having an outer polishing layer 112 and a softer backing layer 114. In some implementations, multiple slurry delivery grooves 116 (see...) Figure 2A A groove 116 is formed in the top surface of the polishing layer 112 of the polishing pad 110. The groove 116 extends partially, but not completely, through the thickness of the polishing layer 112. Typically, the groove has a depth in the range of 25 mils to 30 mils (e.g., 0.025” to 0.030”) from the polishing surface (e.g., the top surface) of the polishing pad 110, and the depth may be lower depending on the wear of the polishing pad after several polishing operations.

[0023] The polishing apparatus 100 may include a port 130 for dispensing polishing fluid 132 (such as polishing slurry) onto the polishing pad 110. The polishing apparatus may also include a polishing pad adjuster to abrade the polishing pad 110 to keep the polishing pad 110 in a consistent polished state.

[0024] The polishing apparatus 100 includes at least one bearing head 140. The bearing head 140 is operable to hold the substrate 10 against the polishing pad 110. Each bearing head 140 can independently control polishing parameters, such as pressure, associated with each respective substrate.

[0025] The support head 140 may include a retaining ring 142 to secure the substrate 10 beneath the flexible membrane 144. The support head 140 also includes one or more independently controllable pressurized chambers defined by the membrane, such as three chambers 146a to 146c, which can apply independently controllable pressure to the flexible membrane 144 and thereby to relevant areas on the substrate 10. Although for ease of illustration... Figure 1 Only three chambers are shown, but there may be one or two chambers, or four or more chambers, such as five chambers.

[0026] The carrier head 140 is suspended on a support structure 150 (e.g., a turntable or track) and connected to a carrier head rotation motor 154 (e.g., a DC induction motor) via a drive shaft 152, allowing the carrier head to rotate about axis 155. Optionally, each carrier head 140 may oscillate laterally, for example, on a slider on the turntable 150, or by the rotational oscillation of the turntable itself, or by sliding laterally along a track. In typical operation, the platform rotates about its central axis 125, and each carrier head rotates about its central axis 155 and translates laterally across the top surface of the polishing pad.

[0027] A controller 190, such as a programmable computer, is connected to motors 121 and 154 to control the rotational speed of platform 120 and bearing head 140. For example, each motor may include an encoder that measures the rotational speed of the associated drive shaft. Feedback control circuitry (which may be in the motor itself, part of the controller, or a separate circuit) receives the measured rotational speed from the encoder and adjusts the current supplied to the motor to ensure that the rotational speed of the drive shaft matches the rotational speed received from the controller.

[0028] When the slurry, polishing pad, or substrate material undergoes deformation during polishing, the vibration of the polishing pad to be monitored may be caused by the release of acoustic energy, and the resulting vibration spectrum is related to the material properties of the slurry, polishing pad, and / or substrate. Without being limited by any particular theory, possible sources of this energy (also known as "stress energy") and its characteristic frequencies include chemical bond breaking, characteristic phonon frequencies, slip-stick mechanisms, etc. Vibrations generated during polishing may include noise (sometimes referred to as acoustic signals) generated by friction between the substrate and the polishing pad, or noise generated by cracks, chips, fractures, or similar defects on the substrate.

[0029] Vibration can be monitored by optically monitoring the displacement of a portion of the polishing pad. Measuring displacement using a light source (e.g., a laser) provides high-precision and high-frequency monitoring of vibration. The optical monitoring system can detect minute displacements on the polishing pad surface at high sampling rates (e.g., greater than 300 kHz), thus facilitating accurate reconstruction of polishing pad vibration. Furthermore, the absence of an intermediate medium or mechanical coupling between the projected light and the bottom surface of the insert 118 allows for direct vibration measurement with minimal or no added noise from air within the recess 117.

[0030] Position sensors, such as optical interruptors or rotary encoders attached to the edge of the platform, can be used to sense the angular position of the platform 120. This allows only a portion of the signal measured when the light source 162 is close to the substrate (e.g., when the light source 162 is under the carrier head or substrate) to be used for endpoint detection.

[0031] The polishing apparatus 100 includes at least one in-situ pad vibration monitoring system 160. Specifically, the in-situ pad vibration monitoring system 160 can be configured to detect vibrations in the polishing pad 110 caused by stress energy when the material of the substrate 10 undergoes deformation. The vibration travels through the backing layer 114 and the polishing layer 112 of the polishing pad 110 and can be detected by the in-situ pad vibration monitoring system 160.

[0032] The in-situ pad vibration monitoring system 160 includes a displacement sensor assembly comprising a light source 162 positioned to direct light onto the bottom surface of the polishing pad, and a sensor 164 for detecting reflections of light from the polishing pad. In some embodiments, the in-situ pad vibration monitoring system 160 includes multiple displacement sensor assemblies to monitor vibration at multiple locations on the polishing pad, for example, at multiple locations equidistant from and / or uniformly spaced around the rotation axis 125.

[0033] exist Figure 1 and Figure 2A In the embodiment shown, the polishing pad 110 includes an insert 118 fixed in and extending through the polishing layer 112, such that the upper surface 119 of the insert 118 is coplanar with the uppermost surface (e.g., polishing surface 112a) of the polishing layer 112, and thus the upper surface 119 will contact the substrate 10 during operation. In some embodiments, as shown in FIG2, the insert 118 extends through the polishing layer and the backing layer 114. In some embodiments, such as Figure 2B In this implementation, the insert extends through the polished layer 112 but not into the backing layer 114. Instead, the pores 114a in the backing layer 114 are located below the insert 118.

[0034] Insert 118 is typically cylindrical, although other shapes are possible. For example... Figure 2AAs shown, the insert 118 may be drum-shaped, having a diaphragm 118a and an annular sidewall 118b extending downward from the outer edge of the diaphragm 118a. The diaphragm 118a may be thinner than the polished layer 112. The thickness of the diaphragm 118a may be between 20% and 90% of the thickness of the polished layer 112. The bottom edge of the sidewall 118b is reliably attached to the top of the platform 120.

[0035] Depending on the situation, such as Figure 2B As shown, a flange 118c (e.g., an annular flange) may extend radially outward from the bottom edge of the annular sidewall 118b. The annular flange 118c may be sandwiched between the polished layer 112 and the backing layer 114, or between the backing layer 114 and the platform 120. In some embodiments, the flange 118c is secured to the backing layer 114 with adhesive or tape to increase the stability of the insert 118 relative to the backing layer 114.

[0036] In some embodiments, the outer diameter (e.g., edge-to-edge) of the insert 118 is in the range of 10 mm to 20 mm (e.g., 12 mm, 14 mm, 16 mm, or 18 mm). The insert 118 includes a recess 117. The diameter of the recess 117 is smaller than the outer diameter of the insert 118 and defines an aperture within the insert 118. The diameter of the recess 117 may be in the range of 8 mm to 18 mm (e.g., 10 mm, 12 mm, 14 mm, or 16 mm). The insert 118 is composed of a material with a hardness similar to the surrounding backing layer 114 and / or polishing layer 112, thus reducing polishing differences when the substrate 10 passes over the insert 118 during a polishing operation. In some embodiments, the insert 118 is made of a material with the same hardness as the backing layer 114 and / or polishing layer 112. In some embodiments, the insert 118 is composed of a material resistant to chemical interactions, such as chemicals present in the liquid 132.

[0037] In some embodiments, one or more layers of the polishing pad 110 are porous, such as the backing layer 114 and / or the polishing layer 112. In the embodiments described above, the insert 118 is a generally non-porous solid material such that vibrations induced at the upper surface 119 are transmitted to the reflective surface 115 without acoustic loss, such as vibrations traveling through a porous medium.

[0038] The upper inner surface of the groove 117 includes a coating or is composed of the material constituting the reflective surface 115. The reflective surface 115 may be provided by a metal foil, metallized coating, or the like on the upper inner surface of the groove 117. In some embodiments, the reflective surface 115 reflects at least 90% of the light from the reflective surface 115 within the optical wavelength range (e.g., at least 90%, at least 92%, at least 95%) used by the in-situ pad vibration monitoring system 160. The insert 118 is configured to structurally connect the upper surface 119 to the reflective surface 115 such that vibrations caused by stress energy are transmitted from the upper surface 119 to the reflective surface 115.

[0039] The thickness of the diaphragm 118a (e.g., the distance between the upper surface 119 and the reflective surface 115) can range from 10 mils to 30 mils (e.g., 0.010” to 0.030”). In some embodiments, the thickness of the upper surface 119 is 20 mils (e.g., 0.020”). The reduced thickness of the diaphragm 118a increases vibration detection sensitivity, while the increased thickness increases the durability of the insert 118 and product life.

[0040] The reflective surface 115 is flat and spans at least a portion of the upper surface of the groove 117, which is parallel to the lower surface of the polishing layer and polishing pad 110. The reflective surface 115 may span the upper surface of the groove 117, ranging from 10% to 100% of the surface area (e.g., 10% or more, 30% or more, 50% or more, 70% or more, 90% or less, 70% or less, 50% or less, 30% or less, 20% or less, or 100%). In some embodiments, the reflective surface 115 may have a width ranging from 8 mm to 18 mm (e.g., 10 mm, 12 mm, 14 mm, or 16 mm).

[0041] Light source 162 emits a beam 163 directed toward reflective surface 115. In some embodiments, beam 163 is continuous, and in alternative embodiments, beam 163 is discontinuous, such as pulsed. In some embodiments, light source 162 emits a single-wavelength collimated beam 163; for example, light source 162 is a laser. In-situ pad vibration monitoring system 160 includes sensor 164 positioned to receive the beam 163 scattered from reflective surface 115. Vibration from diaphragm 118a is translated into displacement of reflective surface 115. This displacement changes the position where sensor 164 receives the beam 163. Sensor 164 generates a signal based on the received beam 163. Sensor 164 electronically communicates with and transmits signals to circuitry 168.

[0042] Sensor 164 can be connected to a power supply and / or other signal processing electronics 166 via a rotational coupling (e.g., a mercury slip ring) through circuitry 168. Signal processing electronics 166 can then be connected to controller 190. In some implementations, the signal from sensor 164 can be amplified by a built-in internal amplifier. If necessary, the signal from sensor 164 can then be further amplified and filtered, and digitized via an A / D port to, for example, a high-speed data acquisition board in signal processing electronics 166. Data from sensor 164 can be recorded at frequencies from 100 kHz to 400 kHz. In some implementations, data from sensor 164 is collected at a frequency of 392 kHz. Data collected at higher rates (e.g., greater than 100 kHz) provides information about higher-frequency vibrations and increases the reproduction of lower-frequency components in the vibrations.

[0043] In some implementations, the light source 162, sensor 164, circuit system 168, and / or signal processing electronics 166 are included in a single instrument, such as, for example, the LK-G5000 sensor head and controller manufactured by Keyence.

[0044] exist Figure 2C In this embodiment, a groove 117 is formed within the polished layer 112 itself, rather than in a separate insert. The upper inner surface of the groove 117 is provided with a reflective surface 115. In this embodiment, the reflective surface 115 and the polished layer 112 above the groove 117 are continuous. The depth of the groove 117 is between 10% and 80% of the thickness of the polished layer 112. Lower values ​​provide increased durability of the polished layer 112 above the groove 117, while higher values ​​provide increased signal from the beam 163, as detected by sensor 164. In some embodiments, the polishing pad 110 includes a portion located above the groove 117, said portion being made of a non-porous material to reduce vibration signal noise, for example, via reflection and attenuation.

[0045] Additionally, refer to Figure 3 A top view of the polishing pad 110 is illustrated as including a groove 116, an insert 118, and a portion 180 of a polishing layer 112 surrounding the insert 118. In some embodiments, the portion 180 is flat, i.e., without a groove, and coplanar with the top surface of the surrounding polishing layer 112. The implementation including the portion 180 surrounding the insert 118 reduces vibrations transmitted via the insert 118 due to interaction with the edges of the groove 116 of the remaining polishing pad 110. In some embodiments, the portion 180 is composed of the same material as the insert 118. In some alternative embodiments, the portion 180 is composed of a non-porous material, such as the material of the insert 118.

[0046] The insert 118 and the in-situ pad vibration monitoring system 160 below it may be located at the center of the platform 120, such as at the rotation axis 125, at the edge of the platform 120, or at the midpoint (e.g., 5 inches from the rotation axis for a 20-inch diameter platform).

[0047] When portion 180 of the polishing pad rotates below substrate 10, see Figure 1 and Figure 3 The adhesive / slip action (e.g., stress energy release) between portion 180 and substrate 10 will result in vibration characteristics. However, since portion 180 and sensor 164 are independent of the rest of polishing pad 110 and platform 120, the sensor can selectively pick up vibration behavior from portion 180 of the pad.

[0048] The signal received by sensor 164 from light source 162 (e.g., after amplification, preliminary filtering, and digitization) may undergo data processing in controller 190 for endpoint detection or feedback or feedforward control. In some implementations, controller 190 determines the exposure of the underlying layer.

[0049] In some implementations, frequency analysis of the signal is performed. For example, a Fast Fourier Transform (FFT) can be performed on the signal to generate a spectrum. Specific frequency bands can be monitored, and if the intensity in the band exceeds a threshold, it can indicate the exposure of the underlying layer, which can then be used to trigger an endpoint. Alternatively, if the width of a local maximum or minimum value within a selected frequency range exceeds a threshold, this can also indicate the exposure of the underlying layer, which can then be used to trigger an endpoint.

[0050] As another example, a wavelet packet transform (WPT) can be performed on the signal to decompose it into low-frequency and high-frequency components. If necessary, the decomposition can be iterated to break the signal down into even smaller components. The intensity of one of the frequency components can be monitored; if the intensity of that component exceeds a threshold, it indicates that the underlying layer is exposed, which can then be used to trigger an endpoint.

[0051] The detection of the polishing endpoint triggers the cessation of polishing, although polishing may continue for a predetermined amount of time after the endpoint is triggered. Alternatively or additionally, the collected data and / or the endpoint detection time may be fed forward to control substrate processing in subsequent processing operations, such as polishing at a subsequent station, or may be fed back to control the processing of subsequent substrates at the same polishing station.

[0052] Figure 4A flowchart illustrating the steps for determining the exposure of a coating layer on a substrate using reflected optical signals for the icon. The substrate is polished using a polishing pad (step 402). This step includes holding the substrate in a carrier head and bringing the substrate into contact with the polishing surface, and generating relative motion between the substrate and the polishing pad, for example, by means of a rotating platform and the carrier head. When relative motion occurs between the substrate and the polishing pad, energy is released between the slurry and the polishing pad, or the substrate material deforms during polishing, and the resulting vibrational spectrum is transmitted from the polishing surface to the underside of the polished layer.

[0053] A light source generates a light beam (step 404), which is directed at the reflective surface 115 at the bottom of the polishing pad 110. A sensor receives the reflected light beam (step 406) and generates a signal based on the received reflected light beam.

[0054] Controller 190 determines the exposure of the sublayer of substrate 10 based on the vibration spectrum (step 408). This determination may include performing a Fast Fourier Transform (FFT) or Wavelet Packet Transform (WPT) on the signal to determine the vibration spectrum. For example, total power within a preset wavelength range may be monitored. If controller 190 detects that the monitored power exceeds a preset threshold, controller 190 may generate a signal indicating sublayer exposure. In response to the signal, controller 190 modifies the processing, such as stopping polishing, changing the pressure applied to the substrate, or modifying the supplied polishing slurry. In-situ pad vibration monitoring system 160 and / or controller 190 may perform additional or alternative data processing on the signal or the vibration spectrum as described herein.

[0055] The implementations and all functional operations described herein can be implemented in digital electronic circuit systems or computer software, firmware, or hardware, including the structural components disclosed herein and their structural equivalents, or combinations thereof. The implementations described herein can be implemented as one or more non-transitory computer program products, i.e., one or more computer programs tangibly implemented in a machine-readable storage device for execution by or control of the operation of a data processing device, such as a programmable processor, computer, or multiple processors or computers.

[0056] Computer programs (also called programs, software, software applications, or code) can be written in any programming language, including compiled or interpreted 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. A computer program does not necessarily correspond to a file. A program may be stored as part of a file containing other programs or data, in a single file dedicated to the program in question, or in multiple coordinating files (e.g., a file storing one or more modules, subroutines, or portions of code). Computer programs can be deployed to execute on a single computer or multiple computers at a single location, or distributed across multiple locations and interconnected via a communication network.

[0057] The processes and logic flows described in this specification can be executed by one or more programmable processors, which execute one or more computer programs to perform functions by manipulating input data and generating outputs. The processes and logic flows can also be executed by a dedicated logic circuit system, and the device can be implemented as a dedicated logic circuit system, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

[0058] The term "data processing device" encompasses all devices, apparatuses, and machines used for processing data, including, for example, programmable processors, computers, or multiple processors or computers. In addition to hardware, the device may also include code that creates an execution environment for the computer program in question, such as code constituting processor firmware, protocol stacks, database management systems, operating systems, or combinations thereof. Processors suitable for executing computer programs include, for example, general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer.

[0059] Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, such as semiconductor memory devices, such as erasable programmable read-only memory (EPROM), electronically erasable programmable read-only memory (EEPROM), and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD-ROMs and DVD-ROMs. Processors and memory may be supplemented by or incorporated into dedicated logic circuitry systems.

[0060] The polishing equipment and methods described above can be applied to a variety of polishing systems. The polishing pad or carrier head, or both, can be movable to provide relative movement between the polishing surface and the wafer. For example, the platform may travel about a track rather than rotate. The polishing pad may be a circular (or some other shape) pad fixed to the platform. Certain aspects of the endpoint detection system may be applicable to linear polishing systems (e.g., where the polishing pad is a continuously or linearly moving roll-to-roll). The polishing layer may be a standard (e.g., polyurethane with or without filler) polishing material, a soft material, or a fixed abrasive material. Using the terminology of relative positioning; as understood, the polishing surface and the wafer may be held in a vertical direction or some other orientation.

[0061] Although this specification contains numerous specific implementation details, these details should not be construed as limiting the scope of any invention or the scope that may be claimed, but rather as descriptions of features that may be specific to particular embodiments of a particular invention. Some features described in this specification in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Furthermore, although features may be described above as functioning in certain combinations, or even initially claimed, in some cases one or more features from a claimed combination may be removed from the combination, and the claimed combination may be for sub-combinations or variations thereof.

[0062] Similarly, although the operations are depicted in the accompanying drawings and described in a specific order in the claims, this should not be construed as requiring the operations to be performed in the specific order shown or sequentially, or that all shown operations be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various system modules and elements in the above embodiments should not be construed as requiring such separation in all embodiments, but rather it should be understood that the described program elements and systems can generally be integrated into a single software product or packaged into multiple software products.

[0063] Specific embodiments of this subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims may be performed in different orders, but the desired result may still be achieved. As an example, the process shown in the figures does not necessarily require the specific order or sequence shown to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous.

Claims

1. A chemical mechanical polishing apparatus, comprising: platform; A polishing pad supported by the platform, the polishing pad including a recessed region, wherein the upper surface of the recessed region extends from and is coplanar with the surrounding polishing surface of the polishing pad, and the lower surface of the recessed region has a reflective surface that is parallel to the polishing surface and the lower surface of the polishing pad and recessed from the lower surface of the polishing pad; A support head for holding the substrate against the polishing surface of the polishing pad; An electric motor is used to generate relative motion between the platform and the support head in order to polish the overlay on the substrate; An in-situ pad vibration monitoring system, the in-situ pad vibration monitoring system including a light source for emitting a light beam and a sensor for receiving reflections of the light beam from the reflective surface of the polishing pad; as well as A controller configured to detect exposure of the polished underlayer of the substrate attributable to the substrate based on measurements from the sensors of the in-situ pad vibration monitoring system, the measurements indicating vibration of the reflective surface in a direction perpendicular to the lower surface of the polishing pad.

2. The device of claim 1, wherein the polishing pad includes an insert, and the upper surface of the insert is coplanar with the upper surface of the polishing pad, and the reflective surface is accommodated within the insert.

3. The apparatus of claim 2, wherein the polishing pad comprises a porous material and the insert comprises a non-porous material.

4. The device of claim 2, wherein the distance between the upper surface of the insert and the reflective surface is in the range of 10 mils to 30 mils.

5. The device of claim 2, wherein the reflective surface of the insert has a width ranging from 8 mm to 18 mm.

6. The device of claim 2, wherein the insert has a hardness within 10 Shore hardness values ​​of the polishing pad hardness value.

7. The apparatus of claim 2, wherein the polishing pad has a polishing layer and a plurality of slurry delivery grooves in the polishing surface of the polishing layer, and wherein the insert is located in a portion of the polishing pad lacking the slurry delivery grooves.

8. The device of claim 1, wherein the controller is configured to: Frequency domain analysis is performed on the measurements received from the sensors of the in-situ pad vibration monitoring system.

9. The device of claim 8, wherein the sensor is configured to monitor the polishing endpoint based on the frequency domain analysis.

10. The device of claim 1, wherein the sensor is configured to respond to the measurement from the sensor of the in-situ pad vibration monitoring system: Adjust the current pressure of the bearing head; or Adjust the baseline pressure for subsequent polishing of the new substrate.

11. The device of claim 1, wherein the sensor is configured to receive a reflected light beam at a frequency of 250 kHz or greater.

12. The device of claim 1, wherein the sensor is configured to receive a reflected light beam at a frequency of 395 kHz or greater.

13. A method comprising the following steps: Relative motion is generated between a substrate and a polishing pad of a chemical mechanical polishing apparatus, wherein the polishing pad includes a recessed region, the upper surface of the recessed region extends from and is coplanar with the surrounding polishing surface of the polishing pad, and the lower surface of the recessed region has a reflective surface that is parallel to the polishing surface and the lower surface of the polishing pad and recessed from the lower surface of the polishing pad. Generate a light beam, wherein the light beam is reflected from the reflective surface of the polishing pad; The reflected light beam is received using the sensor of the chemical mechanical polishing equipment; Vibration of the reflective surface in a direction perpendicular to the lower surface of the polishing pad is detected from the reflected light beam; as well as The polishing endpoint of the substrate supported by the chemical mechanical polishing equipment is determined based on the detected vibrations.

14. The method of claim 13, further comprising the step of: determining the frequency domain analysis of the reflected beam.

15. The method of claim 14, wherein the step of determining the polishing endpoint is based on the frequency domain analysis.

16. The method of claim 14, wherein the step of determining the frequency domain analysis comprises the steps of performing a Fast Fourier Transform (FFT) or a Wavelet Packet Transform (WPT).

17. The method of claim 14, further comprising the following steps: Adjust the current pressure of the bearing head; or The baseline pressure for subsequent polishing of the new substrate is adjusted based on the frequency domain analysis.

Images