Chemical Mechanical Polishing Apparatus and Method

This application is a continuation of U.S. Non-provisional patent application Ser. No. 18/341,090, titled “Chemical Mechanical Polishing Apparatus and Method,” filed on Jun. 26, 2023, which is a continuation of U.S. Non-provisional patent application Ser. No. 16/502,845, titled “Chemical Mechanical Polishing Apparatus and Method,” filed on Jul. 3, 2019 and issuing as U.S. Pat. No. 11,738,423 on Aug. 29, 2023, which claims the benefit of U.S. Provisional Patent Application No. 62/712,378, titled “Novel Chemical Mechanical Polishing Apparatus and Method,” filed on Jul. 31, 2018, all of which are incorporated herein by reference in their entireties.

Polishing pad conditioners in wafer polishing equipment “re-energize” a polishing pad's surface and extend the polishing pad's lifetime by ensuring consistent chemical mechanical planarization (CMP) processes. However, the polishing performance of the polishing pad deteriorates over time even with the use of polishing pad conditioners. The gradual deterioration of the polishing pad's performance can lead to a polishing variation across wafers that have been polished between the beginning and the end of the polishing pad's lifetime . . .

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed that are between the first and second features, such that the first and second features are not in direct contact.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

The term “nominal” as used herein refers to a desired, or target, value of a characteristic or parameter for a component or a process operation, set during the design phase of a product or a process, together with a range of values above and/or below the desired value. The range of values is typically due to slight variations in manufacturing processes or tolerances.

The term “substantially” as used herein indicates the value of a given quantity that can vary based on a particular technology node associated with the subject semiconductor device. In some embodiments, based on the particular technology node, the term “substantially” can indicate a value of a given quantity that varies within, for example, ±5% of a target (or intended) value.

The term “about” as used herein indicates the value of a given quantity that can vary based on a particular technology node associated with the subject semiconductor device. In some embodiments, based on the particular technology node, the term “about” can indicate a value of a given quantity that varies within, for example, 5-30% of the value (e.g., ±5%, ±10%, ±20%, or ±30% of the value).

The term “vertical,” as used herein, means nominally perpendicular to the surface of a substrate.

Chemical mechanical planarization (CMP) is a wafer surface planarization technique that planarizes the wafer's surface by relative motion between the wafer and a polishing pad in the presence of a slurry while applying pressure (downforce) to the wafer. The CMP tool is referred to as a “polisher.” In the polisher, the wafer faces down on a wafer holder, or carrier. An opposite wafer surface is held against a polishing pad positioned on a flat surface (referred to as a “platen”). Polishers can use either a rotary or orbital motion during the polishing process. CMP achieves wafer planarity by removing elevated features on the wafer's surface relative to recessed features. The slurry and the polishing pad are referred to as “consumables” because of their continuous usage and replacement; their condition needs to be continuously monitored.

The slurry is a mixture of fine abrasive particles and chemicals that are used to remove specific materials from the wafer's surface during the CMP process. Precise slurry mixing and consistent batch blends are critical for achieving wafer to wafer (WtW) and lot to lot (LtL) polishing repeatability (e.g., consistent polishing rate, consistent polishing uniformity across the wafer and across the die, etc.). The quality of the slurry is important so that scratches on the wafer surface are prevented during the CMP process.

The polishing pad attaches to a top surface of the platen. The polishing pad can be made, for example, from polyurethane due to polyurethane's mechanical characteristics and porosity. Further, the polishing pad can feature small perforations (e.g., grooves) to help transport the slurry along the wafer's surface and promote uniform polishing. The polishing pad also removes the reacted products away from the wafer's surface. As the polishing pad is used to polish more wafers, the polishing pad's surface becomes flat and smooth, causing a condition referred to as “glazing.” Glazed pads cannot hold the polishing slurry-which significantly decreases the polishing rate and polishing uniformity on the wafer.

Polishing pads require regular conditioning to retard the effects of glazing. The purpose of conditioning is to extend the polishing pad's lifetime and provide consistent polishing performance throughout its life. Pads can be conditioned with mechanical abrasion or a deionized (DI) water jet spray that can agitate (activate) the polishing pad's surface and increase its roughness. An alternative approach to activate the polishing pad's surface is to use a conditioning wheel (“disk”) featuring a bottom diamond surface that contacts the polishing pad while it rotates. The conditioning process inevitably removes pad surface material and it is a significant factor in the polishing pad's lifetime. Conditioning can be performed either in-situ (internal) or ex-situ (external) of the CMP tool. In in-situ conditioning, the conditioning process is performed in real-time, where the polishing pad conditioning wheel or disk is applied to one portion of the polishing pad while the wafer polishing occurs on another portion of the polishing pad. In ex-situ pad conditioning, the conditioning is not performed during polishing but only after a predetermined number of wafers is polished. Eventually the polishing pad will have to be replaced. For example, 3000 or more wafers can be processed before the polishing pad is replaced.

Pad conditioning however has its challenges and it is not a straightforward process. For example, as the polishing pad is conditioned over its lifetime, the polishing pad's surface becomes increasingly uneven-more so at the edges of the polishing pad-due to inherent mechanical limitations (e.g., the size of the wheel or disk). Further, the polishing pad's surface can become uneven (e.g., non-planar) as it polishes an increasing number of wafers. Therefore, during conditioning, if the wheel exerts the same downforce to all the features of an uneven surface, the surface uniformity of the polishing pad will not improve over time. For instance, the uneven profile (e.g., surface contour) of the polishing pad's surface will propagate through the polishing pad's volume as pad material is removed from its surface during the conditioning process. Consequently, as the polishing pad is repeatedly conditioned, its polishing ability (removal rate) deteriorates through its lifetime. In other words, the polishing pad's lifetime and performance is impacted, which in turn increases the CMP cost and yield loss.

The present disclosure is directed to a method and apparatus that utilize a multiple layer (“multilayer”) polishing pad and a laser unit configured to remove a non-planar top polishing pad layer of the multiple layer polishing pad as means to condition the multiple layer polishing pad, extend the polishing pad's lifetime, and provide a consistent wafer polishing performance throughout the polishing pad's lifetime. In some embodiments, the laser unit is configured to produce a laser with a wavelength range between about 400 nm and about 700 nm (e.g., about 532 nm). In other embodiments, the laser beam is configured to burn the top polishing pad layer of the multilayer polishing pad to reveal an unused (or fresh) under-layer. The fresh layer can be substantially planar compared to the removed layer and can thus reset the polishing rate and polishing uniformity of the CMP process.

is an isometric view of selected components of an exemplary CMP polisher(also referred to herein as “polisher”), according to some embodiments. Polisherincludes a polishing pad(also referred to herein as “pad”) which is loaded on a rotating platen (e.g., a rotating table). Polisheralso includes a rotating wafer carrierand a slurry feeder. For illustration purposes,includes selected portions of polisherand other portions (not shown) may be included, such as chemical delivery lines, drain lines, control units, transfer modules, pumps, etc. A waferto be polished is mounted face-down (e.g., with its top surface facing down) at the bottom of wafer carrierso that the wafer's top surface contacts the top surface of pad. Wafer carrierrotates waferand exerts pressure (e.g., downforce) on it so that waferis pressed against rotating pad. Slurry, which includes chemicals and abrasive particles, is dispensed on the polishing pad's surface. Chemical reactions and mechanical abrasion between slurry, wafer, and padcan result in material removal from the top surface of wafer.

In some embodiments, platenand wafer carrierrotate in the same direction (e.g., clockwise or counter clockwise) but with different angular speeds (e.g., rotating speeds). At the same time, wafer carriercan swing between the center and the edge of pad. However, the aforementioned relative movements of the various rotating components, such a wafer carrierand platen, are not limiting.

In some embodiments, the physical and mechanical properties of pad(e.g., roughness, material selection, porosity, stiffness, etc.) depend on the material to be removed from wafer. For example, copper polishing, copper barrier polishing, tungsten polishing, shallow trench isolation polishing, oxide polishing, or buff polishing require different types of pads in terms of materials, porosity, and stiffness. The polishing pads used in a polisher (e.g., polisher) should exhibit some rigidity in order to uniformly polish the wafer surface. Polishing pads (e.g., pad) can be a stack of soft and hard materials that can conform to some extent to the local topography of wafer. By way of example and not limitation, padcan include porous polymeric materials with a pore size between about 1 μm and about 500 μm.

According to some embodiments,is a magnified, cross-sectional viewof an exemplary “used” pad(also shown in). A thickness profileof padcan be the result of the continuous polishing action of padon wafers (e.g., wafer). In some embodiments, the height difference between a “high” pointA and a “low” pointB on the polishing pad's top surfacecan be as much as 0.1 mm (e.g., H2-H1≤0.05 mm). The height of each point (e.g., “high” pointA and “low” pointB) on top surfaceis measured in reference to the polishing pad's substantially planar bottom surface, as shown in. If padcontinues to polish wafer, thickness profileof padwill become more pronounced. For example, the height difference between high point A and low point B will increase. As a result of this process, polishing padwill lose its polishing ability and it will produce poor uniformity across wafer.

is an isometric view of selective components of an exemplary CMP polisher(also referred to herein as “polisher”), according to some embodiments. Polisherincludes a multilayer polishing padon a rotating platen, a rotating wafer carrier, and a slurry feeder. Further, polisheris equipped with a laser unit. In some embodiments, laser unitis configured to produce a laser beamcapable of removing a top layer of multilayer polishing pad. Laser beamhas a wavelength between about 400 nm and 700 nm. More specifically, the wavelength of laser beamcan range between the ultraviolet and the infrared spectrums. In some embodiments, laser beamproduced by laser unit, is substantially parallel to the surface of multilayer polishing pad, as shown in. In some embodiments, laser beamscans the surface of multilayer polishing pad, while multilayer polishing padrotates. As a result, laser beamremoves the non-planar layer (e.g., top layer) of multilayer polishing padand reveals an unused (or fresh) substantially flat under-layer.

In some embodiments, multilayer polishing padincludes 4 or more individual polishing pad layers (e.g., 4, 6, 10, or more) made from a polymer material. By way of example and not limitation, laser beamcan remove the top polishing pad layer of the multilayer polishing padwhen the surface uniformity of the top polishing pad layer is not acceptable—for example, when the removal rate for polishing materials on waferdrops below an allowable level or when the CMP non-uniformity on waferincreases beyond acceptable levels. In some embodiments, a sensor, which can be located over multilayer polishing pad, is configured to monitor the thickness of the top polishing pad layer of multilayer polishing padand to indicate to a system (not shown in) when the top polishing pad layer of multilayer polishing padneeds to be removed by laser unit. By way of example and not limitation, sensorcan be an optical sensor (e.g., a camera, a laser, an infrared (IR) sensor, etc.) or an acoustic sensor (e.g., ultrasound sensor). In some embodiments, sensoris configured to be stationary with respect to the position of multilayer polishing pador to move along a plane parallel to multilayer polishing padat a fixed height from the top surface of multilayer polishing pador platen.

As discussed above, multilayer polishing padincludes multiple polishing pad layers. For example, and referring to, multilayer polishing padcan include individual polishing pad layersA,B,C, andD arranged on top of each other with a separation layerbetween adjacent polishing pad layers. The number of layers in multilayer polishing padmay not be limited to the example of, and thus multilayer polishing padcan include fewer or additional individual polishing pad layers. In some embodiments, multilayer polishing padcan include from 4 to 10 or more individual polishing pad layers (e.g., 4, 6, 8, 10, or 15). By way of example and not limitation, the polishing pads layers in multilayer polishing padshare a common diameter D that can range from about 20 inches to about 32 inches, according to some embodiments. Further, thickness T of each polishing pad layer can range from about 20 mil (e.g., about 0.508 mm) to about 25 mil (e.g., about 0.635 mm), where 1 mil is equal to 0.001 inches or 0.0254 mm. By way of example and not limitation, the total thickness of multilayer polishing padcan range between about 80 mil and about 120 mil. Therefore, depending on the thickness of each polishing pad layer, the multilayer polishing pad can include four or more sacrificial polishing pad layers (e.g., layersA,B,C, andD).

According to some embodiments, each polishing pad layer (e.g.,A,B,C, andD) is a disc made of a polymer with a grooved top surface (not shown in), which helps transport the polishing slurry along the wafer's surface and promotes uniform polishing. Additionally, the polishing pad layers can be porous or solid, hard or soft, depending on the application. By way of example and not limitation, the polishing pad layers can be used to polish metals, dielectrics, glass, ceramics, plastics, etc.

In some embodiments, in referring to, separation layerhas a thicknessT that ranges from about 0.2 mm to about 0.5 mm (e.g., about 0.2 mm). By way of example and not limitation, separation layeris also a disc with a diameter D (e.g., substantially equal to sacrificial polishing pad layersA,B,C, andD). In some embodiments, separationis a glue layer or a bonding layer that holds the sacrificial polishing pad layers together. By way of example and not limitation, separation layercan be made of a polymer material. According to some embodiments, laser beamremoves separation layerfaster than sacrificial polishing pad layersA,B,C, andD. For example, laser beamcan remove separation layerabout 10 times faster than the sacrificial polishing pad layers of multilayer polishing pad.

In some embodiments, top polishing pad layerA of multilayer polishing paddevelops a non-planar (e.g., a non-uniform) thickness profile due to its continuous polishing action on wafershown in. As a result, the polishing rate of top polishing pad layerA decreases, and the polishing uniformity achieved on polished wafergradually deteriorates. The non-planar, or non-uniform, thickness profile starts to appear when points on the surface of top polishing pad layerA develop an elevation difference (e.g., a vertical distance difference) measured from a common reference point. When the vertical distance between two points on the surface of top polishing pad layerA exceeds a limit (e.g., a threshold), the resulting thickness uniformity becomes substantial to the extent it impacts the polishing performance of top polishing pad layerA. In some embodiments, and referring to, the uniformity of the thickness profile of top polishing pad layerA can be determined by vertical distance Va between point A and point B on the surface of top polishing pad layerA. In some embodiments, point A and point B are respectively the highest and lowest points among all surface points on top polishing pad layerA. In other words, point A is a “global” high surface point, and point B is a “global” low surface point. By way of example or limitation, the height or the elevation of each surface point on top polishing pad layerA can be measured from a common reference point—for example, from the bottom surface of the top polishing pad layer, from the bottom surface of the multi-layer polishing pad, or form another reference point. For example, the height, or elevation, of surface points A and B incan be measured either from bottom surfaceof top polishing pad layerA, from bottom surfaceof multilayer polishing pad, or from another suitable reference point.

In some embodiments, the thickness non-uniformity of top polishing pad layerA is determined by a vertical distance Va between global high surface point A and global low surface point B. In some embodiments, the vertical distance Va between global high surface point A and global low surface point B is the maximum vertical distance between any two surface points on top polishing pad layerA.

When the polishing uniformity achieved on waferis no longer within an acceptable range, top polishing pad layerA can be removed to reveal a substantially planar underlying polishing pad layerB. In some embodiments, removal of top polishing pad layerA is achieved with laser beam(shown in) produced by laser unit(shown in). For example, and referring to, laser beamcan remove the non-planar top polishing pad layerA and separation layerto reveal underlying polishing pad layerB, as shown in. In some embodiments, underlying layerB is a “fresh” layer that has a substantially planar top surface. Therefore, the polishing capability of multilayer polishing padcan be restored in terms of polishing rate and polishing uniformity on wafer. According to some embodiments, removal of top polishing pad layerA means that top polishing pad layerA and separation layercan be “burned-off” or trimmed by laser beam. The result of the aforementioned removal operation is shown in.

Over time, the top surface of polishing pad layerB will also become non-uniform. At that point, laser beamcan be used to remove polishing pad layerB and separation layerto expose a fresh polishing pad layerC. This process can be repeated until the last polishing pad layer (e.g., polishing pad layerD) is exposed and used in wafer polishing. When polishing pad layerD is consumed and its top surface becomes non-planar, multilayer polishing padcan be discarded and replaced with a new multilayer polishing pad.

is an exemplary methodfor removing a polishing pad layer of a multilayer polishing pad with a laser beam, according to some embodiments. This disclosure is not limited to this operational description. It is to be appreciated that additional operations may be performed. Moreover, not all operations may be needed to perform the disclosure provided herein. Further, some of the operations may be performed simultaneously, or in a different order than shown in FIG.. In some implementations, one or more other operations may be performed in addition to or in place of the presently described operations. For illustration purposes, methodis described with reference to the embodiments of. However, methodis not limited to these embodiments.

In some embodiments, a system, not shown in, is configured to perform the operations of methodand to coordinate the operation of sensor, laser unit, nozzle, and other components of polisher. By way of example and not limitation, the system can include one or more computer units with appropriate software and hardware, controllers, wireless or wired communication units, and other electronic equipment.

Exemplary methodbegins with operation, where a sensor (e.g., sensorshown in) monitors the thickness profile of a polishing pad layer in a multilayer polishing pad. According to some embodiments, the polishing pad layer can be top polishing pad layerA of a multilayer polishing padshown in. In some embodiments, the thickness profile of top polishing pad layerA is monitored by measuring with sensorthe elevation (e.g., the height) of a fixed number of surface points (e.g., 5, 10, 15, 20, 30, 50, 60, or more) on top polishing pad layerA, and calculating a height difference (e.g., a vertical distance Va) between pairs of the measured surface points. As discussed above, the height measurement or elevation measurement of each surface point is taken with respect to a common reference point or location such as bottom surfaceof top polishing layerA, bottom surfaceof multilayer polishing pad, or another suitable reference point or location. The maximum vertical distance Va between any two surface points on top polishing pad layerA corresponds to the vertical distance between a global high surface point (e.g., the point A) and a global low surface point (e.g., the point B) shown in. In some embodiments, the vertical distance Va between a global high surface point and a global low surface point correlates to the thickness non-uniformity of top polishing pad layerA. For example, the larger the vertical distance Va between a global high surface point and a global low surface point, the larger the thickness non-uniformity of top polishing pad layerA. In some embodiments, the thickness profile of top polishing pad layerA correlates to the polishing pad's “polishing performance.” For example, the polishing performance of the top polishing pad layerA deteriorates as the thickness profile of the top polishing pad layerA becomes less uniform.

In some embodiments, sensoris configured to measure vertical distances between pairs of surface points in the range of about 0.051 mm and 0.254 mm.

In some embodiments, the larger the number of measured points by sensor, the more accurate the assessment on the thickness profile of the top polishing pad layer. However, the number of measured points needs to be balanced between accuracy and measurement efficiency, so that the measurement does not impact the polisher's throughput. In some embodiments, the duration of the measurement ranges from about 20 s to about 70 s (e.g., about 60 s). By way of example and not limitation, the measurement frequency can be adjusted. For example, the measurement can be performed prior or after each polishing operation, after a certain number of wafers have been polished (e.g., after 2, after 5, after 10, after 25, after 50, after 100, after 1000 wafers, etc.), in real-time during the wafer polishing operation, or at any desirable frequency.

Further, as discussed above, sensorcan be stationary with respect to the position of the polishing pad or it can be configured to move along a plane parallel to multilayer polishing pador platenso that it can hover over the polishing pad and scan the surface of the top polishing pad layer. In some embodiments, during the measurement by sensor, the polishing padis stationary. In some embodiments, during the measurement by sensor, polishing padrotates continuously or in intervals.

In some embodiments, sensorcan include circuitry (e.g., a computational unit), which is configured to perform the vertical distance calculation between pairs of surface points on top polishing pad layerA and to determine the thickness profile uniformity of top polishing pad layerA. As discussed above, the sensorcan be part of a system that includes additional electronic equipment (e.g., control units, computers, wireless or wired communication units, etc.) and/or moving parts (e.g., arms, motors, etc.) responsible for the sensor's operation and movement. In some embodiments, the aforementioned system is configured to control the operation of sensor, laser unit, nozzle, and other components of polisher.

In some embodiments, the sensoris an optical sensor (e.g., a camera, a laser, an infrared (IR) sensor, etc.), an acoustic wave sensor (e.g., ultrasound sensor), or combinations thereof. In some embodiments, polisheris equipped with multiple types of sensors, or multiple sensors of the same type.

In some embodiments, the vertical distance Va between a global high surface point A and a global low surface point B on top polishing pad layerA measured by sensoris compared to a “threshold.” The “threshold,” as described herein, is a vertical distance value-between a global high surface point and a global low surface point on top polishing pad layerA-above which, top polishing pad layerA demonstrates unacceptable polishing performance. In some embodiments, the threshold is about 0.051 mm. For a vertical distance Va that exceeds the threshold, top polishing pad layerA is considered consumed, or at the end of its lifetime, and needs to be replaced. The correlation between the threshold and the polishing pad's polishing performance can be determined, for example, through experimentation and further correlation with additional wafer metrics, such as yield data, electrical data, physical data, or combinations thereof.

Referring to, methodcontinues with operation, where the system determines whether the thickness profile exceeds the threshold. If the system determines that the thickness profile—for example, the vertical distance Va between high global surface point A and low global surface point B shown in—is below the threshold, then operationproceeds to operation, where the system, via sensor, continues to monitor the thickness profile of top polishing pad layerA. In response to the vertical distance Va being above the threshold, then methodcontinues to operation.

In operation, the top polishing pad layerA is rinsed. In some embodiments, the rinsing removes byproducts produced during polishing (e.g., slurry or other abrasives, polishing material from wafer, etc.) from the surface of the top polishing pad layerA. Further, the rinse prepares the top polishing pad layerA for removal. By way of example and not limitation, and in referring to, the rinse operation is provided by nozzle, which dispenses pressurized deionized (DI) water(or other chemicals) on the surface of multilayer polishing pad. In some embodiments, the rinsing can be performed while multilayer polishing padrotates or when multilayer polishing padis stationary. In other embodiments, rinsing multilayer polishing padcan be performed by more than one nozzle. For example, a plurality of nozzles, like nozzle, can be arranged around and/or over polishing pad.

Referring toand operation, the top polishing pad layerA shown inis removed by laser beam. In some embodiments, laser unitis configured to produce a laser beamwith a beam size up to about 3 mm to ensure that a single polishing pad layer is removed. In comparison, a laser beam diameter larger than 3 mm is considered large compared to thickness T of the remaining polishing pad layer (e.g., less than about 0.508 mm or less than about 0.635 mm) and can make the removal process challenging to control. For example, laser beamwith a diameter larger than 3 mm can remove more than the remaining portion of top layerA (e.g., laser beamcan remove portions of underlying layerB). In some embodiments, laser beamproduced by laser unithas a wavelength that ranges from about 400 nm to about 700 nm (e.g., about 532 nm). According to some embodiments, laser unitproduces between about 300 Watts and about 800 Watts of power across all the operating wavelengths (e.g., between about 400 nm and about 700 nm).

Removal of the polishing pad layer is achieved by burning off material from polishing pad layerA. In some embodiments, the removal rate of separation layeris higher than the removal rate of the polishing pad layer to ensure that the underlying polishing pad layerB is free from traces (e.g., residue) of separation layerwhen exposed. As discussed above, laser beamremoves separation layerabout 10 times faster than the polishing pad layer. In some embodiments,shows multilayer polishing padafter operation. As shown in, fresh polishing pad layerB is now exposed and can be used to polish subsequent wafers.

In some embodiments, the removal process of operationis timed based on the vertical distance Va between a global high surface point A and a global low surface point B of top polishing pad layerA shown in. In some embodiments, the removal process is interrupted at predetermined intervals so that sensorcan re-measure the vertical distance Va between a global high surface point A and a global low surface point B of top polishing pad layerA. By way of example and not limitation, top polishing pad layerA is removed when the vertical distance Va between a global high point A and a global low point B, as measured by sensor, has reached a value that corresponds to a fresh polishing pad layer (e.g., substantially equal to or greater than about 80 mil), such as polishing pad layerB shown in.

Methodcan be used until bottom polishing pad layerD is consumed; at that point, multilayer polishing padcan be replaced with another multilayer polishing pad. According to some embodiments, methodachieves a consistent polishing performance compared to single-layer polishing pads, which require frequent conditioning with conditioning wheels or disks. Further, methodcan be tuned so that the threshold is set to a value that balances polishing performance and polishing pad lifetime. For example, for critical polishing processes (e.g., polishing processes that are sensitive to wafer polishing variability) the threshold value of methodcan be set so that the polishing pad layers are removed more frequently to maintain a more consistent polishing performance. Accordingly, for less critical polishing processes (e.g., polishing processes that can tolerate higher wafer polishing variability), the threshold value of methodcan be set so that the polishing pad layers are removed less frequently and their lifetime is extended. In some embodiments, the threshold can be different for polishing pad layers with different hardness. For example, hard polishing pad layers may have a higher or lower threshold than soft polishing pad layers.

The present disclose is directed to a method and apparatus to remove consumable (e.g., sacrificial) polishing pad layers from a multilayer polishing pad. In some embodiments, the polishing pad removal can be performed by a laser unit configured to produce a laser beam having a wavelength that ranges, for example, from about 400 nm to about 700 nm and a beam diameter less than about 3 mm. In some embodiments, the multilayer polishing pad is a stack that includes 4 or more individual polishing pad layers, which can be individually removed by the laser beam. In other embodiments, the laser beam removes the top polishing pad layer (e.g., when the thickness profile of the layer is deemed unacceptable) to reveal an unused (or fresh) polishing pad layer, which can be used to polish subsequent wafers. The fresh polishing pad layer is substantially planar compared to the removed polishing pad layer, thus improving the polishing rate and uniformity of the CMP process.

In some embodiments, a system, includes a polishing pad with a plurality of polishing pad layers, a sensor configured to measure a thickness profile of a top polishing pad layer of the plurality of polishing pad layers, a rinse system configured to rinse a surface of the top polishing pad layer, and a laser unit configured to produce a laser beam to remove the top polishing pad layer.

In some embodiments, a method includes measuring a thickness profile of a top polishing pad layer of a multilayer polishing pad and comparing the thickness profile to a threshold. The method, in response to the thickness profile being above the threshold, rinses the top polishing pad layer of the multilayer polishing pad and removes, after the top polishing pad layer is rinsed, the top polishing pad layer to expose an underlying polishing pad layer of the multilayer polishing pad.

In some embodiments, a system includes a polisher with a multilayer polishing pad, one or more sensors configured to determine a thickness profile of a top polishing pad layer of the multilayer polishing pad, a rinse system configured to rinse the top layer of the multilayer polishing pad, and a laser unit configured to produce a laser beam to remove the top polishing pad layer from the multilayer polishing pad. The system further includes a computer unit configured to compare the thickness profile obtained by the one or more sensors to a value, and in response to the thickness profile being greater than the value, command the laser unit to remove the top polishing pad layer.

It is to be appreciated that the Detailed Description section, and not the Abstract of the Disclosure section, is intended to be used to interpret the claims. The Abstract of the Disclosure section may set forth one or more but not all possible embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the subjoined claims in any way.

The foregoing disclosure outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art will appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.