Chemical Mechanical Polishing Slurry Accumulation Monitoring

Abstract

An apparatus and method for monitoring slurry buildup is disclosed, in which a substrate polishing apparatus includes a surface at least partially covered with a fluorescent material, a light source configured to illuminate the surface, an image sensor configured to image the surface, and a processor coupled to the image sensor and configured to monitor slurry buildup on the surface using data provided by the image sensor.

Description

Technical Field

[0001]

[0001] Embodiments of the present disclosure generally relate to a chemical mechanical polishing (CMP) system used in the manufacture of semiconductor devices. Specifically, embodiments herein relate to monitoring slurry accumulation in a CMP system.

Background Art

[0002] Description of Related Art

[0002] Chemical mechanical polishing (CMP) is commonly used in the manufacture of semiconductor devices to planarize or polish a material layer deposited on a substrate surface. During the CMP process, the substrate is held within a substrate carrier that presses the back side of the substrate against a rotating polishing pad in the presence of a polishing fluid. The material is removed across the entire surface of the material layer of the substrate in contact with the polishing pad by a combination of chemical and mechanical actions provided by the polishing fluid and the relative movement between the substrate and the polishing pad.

[0003]

[0003] The polishing fluid used in the CMP process may include an aqueous solution of one or more chemical components and nanoscale polishing particles suspended in the aqueous solution. Generally, dry residues of the polishing fluid, such as aggregates of polishing particles, accumulate on the surface of components disposed above or in proximity to the polishing pad in other states during the polishing process. For example, dry residues of the polishing fluid often accumulate on the surfaces of CMP system components disposed on the polishing pad when the polishing fluid is dispensed, such as substrate carriers, pad conditioner assemblies, and / or fluid delivery arms. If the accumulated residues are not removed, aggregates of polishing particles may be peeled off from the component surface onto the polishing pad and then cause undesirable damage to the material surface of the substrate being polished thereon. This damage often appears as scratches (e.g., micro-scratches) on the substrate surface, which may adversely affect the performance of the device formed thereon, or in some cases, the device may become inoperable.

[0004] Unfortunately, since the aggregated abrasive particles often form a cement-like layer, it is generally difficult and time-consuming to remove the residues accumulated from the surface of the components. As a result, due to the replacement of consumables and / or preventive maintenance procedures, the downtime of the polishing system is long and frequent, resulting in the undesirable result of manually cleaning the accumulated residues from the surface of the components.

[0005] Therefore, there is a need in the art for an apparatus and method to solve the above problems. SUMMARY OF THE INVENTION

[0006] The present disclosure generally relates to a chemical mechanical polishing (CMP) system used in the manufacture of semiconductor devices. Specifically, embodiments herein relate to monitoring slurry accumulation in a CMP system.

[0007] In one embodiment, a substrate polishing apparatus includes a surface at least partially covered with a fluorescent material, a light source configured to illuminate the surface, an image sensor configured to image the surface, and a processor coupled to the image sensor and configured to monitor slurry accumulation on the surface using data supplied from the image sensor.

[0008] In another embodiment, a slurry accumulation monitoring method includes capturing an image of a surface of a polishing apparatus. The surface is at least partially covered with a fluorescent material. The method includes selecting a region of interest in the image and determining a fluorescence parameter of the region of interest, wherein the value of the fluorescence parameter corresponds to the amount of slurry accumulation on the region of interest.

[0009]

[0009] In yet another embodiment, the substrate polishing apparatus includes a surface at least partially covered with a fluorescent material, a light source configured to illuminate the surface, a sensor configured to measure the fluorescence intensity of an area of interest on the surface, and a non-transitory computer-readable medium storing instructions for a monitoring method. The monitoring method includes polishing a substrate within the substrate polishing apparatus with a slurry. The slurry accumulation on the surface reduces the measurable fluorescence intensity of the area of interest. The method includes switching on the light source and, when the light source is switched on, measuring the fluorescence intensity of the area of interest using the sensor. The method includes comparing the measured fluorescence intensity with a first range and generating an alarm if the measured fluorescence intensity is outside the first range.

[0010]

[0010] To gain a more thorough understanding of the features of the present disclosure described above, a more detailed description of the present disclosure, briefly summarized above, can be obtained by referring to the embodiments. Some embodiments are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings show only typical embodiments of the present disclosure and should not be considered as limiting the scope of the present disclosure, as the present disclosure may admit other equally valid embodiments.

Brief Description of the Drawings

[0011]

Fig. 1A

[0011] A plan view of a polishing apparatus according to one or more embodiments.

Fig. 1B

[0012] A schematic partial cross-sectional side view of FIG. 1A.

Fig. 1C

[0013] A schematic partial cross-sectional side view of FIG. 1A.

Fig. 2

[0014] A diagram showing a method for monitoring slurry accumulation according to one or more embodiments.

Fig. 3

[0015] A schematic diagram showing an exemplary setup for monitoring slurry accumulation on a surface according to one or more embodiments.

Best Mode for Carrying Out the Invention

[0012]

[0016] Embodiments of the present disclosure generally relate to a chemical mechanical polishing (CMP) system used in the manufacture of semiconductor devices. Specifically, embodiments herein relate to monitoring slurry accumulation in a CMP system.

[0013]

[0017] The apparatus and / or method disclosed herein provides for monitoring slurry accumulation on the inner surface of a CMP tool. In conventional CMP processes where slurry accumulation is not monitored, defects caused by slurry residues falling on the wafer surface can be the earliest and perhaps the only indication that cleaning is required. Thus, if a defect that may be caused by slurry accumulation is detected, the tool may be taken offline for cleaning or scheduled for cleaning even if cleaning was not previously planned, and scheduling cleaning in such a way (i.e., based on observation of defects caused by the CMP process) is inefficient, causes wafer scrap, and reduces the throughput of the entire process. In contrast, the apparatus and / or method disclosed herein facilitates scheduling of cleaning based solely on slurry accumulation (e.g., before slurry accumulation causes defects). Scheduling cleaning based solely on slurry accumulation results in more efficient scheduling, increases the throughput of the entire process, and reduces or prevents the occurrence of defects that may be caused by lack of cleaning.

[0014]

[0018] In some alternative CMP processes, to prevent defects that may be caused by slurry accumulation, the CMP tool can be taken offline for cleaning at pre-planned intervals regardless of the actual slurry accumulation. However, this approach can also reduce the throughput of the entire process by performing cleaning of the tool before cleaning is actually required. In contrast, using the apparatus and / or method disclosed herein, cleaning is scheduled only when needed, resulting in more efficient cleaning scheduling while shortening the tool downtime.

[0015]

[0019] The apparatuses and / or methods disclosed herein provide monitoring of slurry accumulation for cleaning only specific regions of a CMP tool, as opposed to conventional approaches that clean various internal surfaces regardless of actual slurry accumulation. Thus, the apparatuses and / or methods disclosed herein provide more efficient cleaning of selected surfaces while shortening tool downtime. Further, by prioritizing the surfaces that most need cleaning, the cleaning process can be optimized for more effective cleaning. The apparatuses and / or methods disclosed herein also provide monitoring of slurry accumulation that helps identify problem areas for future continuous improvement programs.

[0016]

[0020] FIG. 1A is a plan view of a polishing apparatus 100, such as a chemical mechanical polishing (CMP) tool, for processing one or more substrates. The polishing apparatus 100 includes a polishing platform, or base 102, that at least partially supports and houses a plurality of polishing stations 124. For example, the illustrated polishing apparatus 100 includes four polishing stations 124a, 124b, 124c, and 124d. Each polishing station 124 is adapted to polish a substrate held within a carrier head 126.

[0017]

[0021] The polishing apparatus 100 also includes a plurality of carrier heads 126, each configured to carry a substrate. The number of carrier heads may be greater than or equal to the number of polishing stations, for example, four carrier heads or six carrier heads. For example, the number of carrier heads may be two more than the number of polishing stations. This allows polishing by other carrier heads at the remaining portions of the polishing stations while loading and unloading the substrate from two of the carrier heads, improving throughput.

[0018]

[0022] The grinding apparatus 100 also includes a transfer station 122 for loading the substrate onto the carrier head 126 and unloading it from the carrier head 126. The transfer station 122 may include a plurality of load cups 123 (for example, two load cups 123a and 123b), and is adapted to facilitate the transfer of the substrate between the carrier head 126 and a factory interface (not shown) or other device (not shown) by the transfer robot 110. The load cups 123 generally facilitate the transfer between the robot 110 and each of the carrier heads 126.

[0019]

[0023] The stations of the grinding apparatus 100 including the transfer station 122 and the grinding station 124 can be positioned at substantially equal angular intervals around the center of the base 102. This is not essential, but it is possible to reduce the installation area and provide the grinding apparatus 100.

[0020]

[0024] Each grinding station 124 includes a polishing pad 130 supported on a platen 120 (shown in FIGS. 1B - 1C). For the grinding operation, one carrier head 126 is positioned at each grinding station 124. Two additional carrier heads are positioned within the transfer station 122 so that the ground substrate can be exchanged with an unground substrate while other substrates are being ground at the grinding station 124.

[0021]

[0025] The carrier head 126 is adapted to hold the substrate against the polishing surface of the polishing pad 130, and relative movement is provided between the carrier head 126 and the platen 120 to grind the substrate. The relative movement can be rotational, lateral, or some combination thereof, and is provided by at least one of the carrier head 126 and the platen 120. Each carrier head 126 can independently control the grinding parameters (such as pressure) associated with each substrate.

[0022]

[0026] The carrier head 126 is held by a support structure that can move each carrier head along a path that sequentially passes through the first polishing station 124a, the second polishing station 124b, the third polishing station 124c, and the fourth polishing station 124d. Thereby, each carrier head can be selectively positioned on each of the polishing station 124 and the load cup 123.

[0023]

[0027] In some embodiments, each carrier head 126 is coupled to a carriage 108 attached to an overhead track 128. By moving the carriage 108 along the overhead track 128, each carrier head 126 can be positioned over a selected polishing station 124 or load cup 123. The carrier head 126 moving along the overhead track 128 traverses a path passing through each of the polishing stations 124.

[0024]

[0028] In the embodiment shown in FIG. 1A, the overhead track 128 has a circular configuration (shown in phantom lines) that allows the carriage 108 holding the carrier head 126 to selectively orbit above and / or around the load cup 123 and the polishing stations 124. The overhead track 128 may have other configurations including an oval, elliptical, linear, or other suitable orientation. Alternatively, in some embodiments (not shown), the carrier head 126 is suspended from a carousel, and rotation of the carousel moves all of the carrier heads 126 simultaneously along a circular path. Although the polishing apparatus shown herein is equipped with an overhead track, the present disclosure can utilize any suitable polishing apparatus. In one example, the polishing apparatus may have a robot that provides the same function as the overhead track.

[0025]

[0029] As shown in more detail in FIG. 1B, each polishing station 124 of the polishing apparatus 100 includes a spray bar 134 for dispensing a polishing fluid such as a polishing slurry onto the polishing pad 130. As shown in more detail in FIG. 1C, each polishing station 124 of the polishing apparatus 100 includes a pad conditioning device 112 for polishing the polishing surface 131 of the polishing pad 130 to maintain the polishing pad 130 in a consistent polishing state.

[0026]

[0030] As will be described in more detail below, a controller 190, such as a programmable computer, is connected to each motor to independently control the rotational speeds of the platen 120 and the carrier head 126. For example, each motor may include an encoder that measures the angular position or rotational speed of the associated drive shaft. Similarly, the controller 190 is connected to an actuator within each carriage 108 to independently control the lateral movement of each carrier head 126. For example, each actuator may include a linear encoder that measures the position of the carriage 108 along the overhead track 128.

[0027]

[0031] The controller 190 includes a programmable central processing unit (CPU) 192 that is operable with a memory 194 (e.g., a non-volatile memory) and support circuits 196. The support circuits 196 are conventionally coupled to the CPU 192 and include a cache, a clock circuit, an input / output subsystem, a power supply, etc. (and combinations thereof) coupled to various components of the polishing apparatus 100.

[0028]

[0032] In some embodiments, the CPU 192 is one of any form of general-purpose computer processor used in industrial settings (such as a programmable logic controller (PLC), etc.) for controlling various monitoring system components and sub-processors. The memory 194 connected to the CPU 192 is non-transitory and is typically one or more of readily available memories such as random access memory (RAM), read-only memory (ROM), floppy disk drive, hard disk, or any other form of local or remote digital storage device.

[0029]

[0033] As used herein, the memory 194 is in the form of a computer-readable storage medium (such as non-volatile memory) that includes instructions which, when executed by the CPU 192, facilitate the operation of the polishing apparatus 100. The instructions in the memory 194 are in the form of a program product (such as a program implementing the method of the present disclosure, such as a middleware application, a device software application, etc.). The program code may conform to any one of several different programming languages. In one example, the present disclosure may be implemented as a program product stored on a computer-readable storage medium for use with a computer system. One or more programs of the program product define the functions of the embodiments (including the methods described herein).

[0030]

[0034] Exemplary computer-readable storage media include, but are not limited to, (i) non-writable storage media where information is permanently stored (e.g., read-only memory devices in a computer such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips, or any type of solid-state non-volatile semiconductor memory), and (ii) writable storage media where modifiable information is stored (e.g., floppy disks in a diskette drive or hard disk drive or any type of solid-state random access semiconductor memory). Such computer-readable storage media become embodiments of the present disclosure when they convey computer-readable instructions that direct the functions of the methods described herein.

[0031]

[0035] Although controller 190 is shown as a single computer, it may be, for example, a distributed system including multiple independently operating processors and memories. The computer architecture can be adapted to various polishing operations that control the order and timing in which the carrier head is positioned at the polishing stations based on the programming of controller 190.

[0032]

[0036] For example, in the operating mode, the carrier head 126 is sequentially positioned at each of the polishing stations 124a, 124b, 124c, and 124d such that the controller loads the substrate onto one of the carrier heads 126 of the load cup 123 and the substrate is polished sequentially at each polishing station. After polishing at the last station, the carrier head 126 returns to one of the load cups 123 and the substrate is unloaded from the carrier head 126.

[0033]

[0037] FIG. 1B is a schematic partial cross-sectional side view of FIG. 1A showing an exemplary spray bar 134 in combination with a polishing station 124. The polishing apparatus 100 has a housing 101. The housing 101 generally includes a base 102, an upper wall 103, and side walls 104 between the base 102 and the upper wall 103. The base 102, the upper wall 103, and the side walls 104 define a processing region 105 of the polishing apparatus 100.

[0034]

[0038] The carrier head 126 has a housing 129. The carrier head 126 is connected to a column 162 and is connected to an overhead track 128 that extends over the platen 120. The drive system 106 is connected to the carrier head 126 by a drive shaft 107. The drive system 106 provides at least rotational movement to the carrier head 126. The drive system 106 can also provide lateral movement to the carrier head 126, for example by driving a carriage 108 on the overhead track 128, to cause the carrier head 126 to move in an arc relative to the platen 120. The carrier head 126 is operable toward and away from the platen 120 such that a substrate 114 held within the carrier head 126 can be positioned with the polishing pad 130 behind it during polishing.

[0035]

[0039] The platen 120 of each polishing station 124 is rotatable about an axis 121. For example, a motor 160 rotates a drive shaft 125 to rotate the platen 120. The platen 120 is rotatably disposed on the base 102. A bearing 158 is disposed between the platen 120 and the base 102 to facilitate rotation of the platen 120 relative to the base 102.

[0036]

[0040] During operation, the platen 120 rotates about the axis 121, and each carrier head 126 rotates about its respective axis 127 and translates laterally across the polishing surface 131. The lateral sweep is in a direction parallel to the polishing surface 131. The lateral sweep may be a linear movement or an arcuate movement.

[0037]

[0041] Each spray bar 134 delivers a polishing fluid, such as slurry 135, to an associated polishing pad 130 to facilitate the polishing operation of the substrate. Additionally, the spray bar 134 may deliver a cleaning fluid (e.g., deionized water) to the polishing pad 130 to wash away polishing by-products from the polishing surface 131. As shown in FIG. 1B, the spray bar 134 includes an arm 136 having a distal end with a plurality of fluid distribution ports (not shown) for spraying a fluid, such as slurry 135, onto the polishing surface 131. The proximal end of the arm 136 is connected to a base 138 that extends upward from the base 102 of the housing 101. The base 138 is rotatable to pivot the arm 136 between a first position (shown in FIG. 1B) disposed on the platen 120 and a second position disposed adjacent to the platen 120. During polishing, the spray bar 134 is positioned at the first position, and as the platen 120 rotates, the slurry 135 is applied onto the polishing surface 131.

[0038]

[0042] The spray bar 134 is fluidly connected to one or more fluid sources outside the processing region 105, such as a slurry source 140 and a deionized water source 142. Although only the slurry source and the deionized water source are shown, the spray bar 134 may utilize a number of additional fluid chemistries, as is known in the art. For example, other suitable fluid chemistries may include alcohols, amphiphilic compounds (e.g., detergents, soaps, lipoproteins, surfactants, synthetic amphiphilic substances, natural amphiphilic substances), acids (e.g., citric acid, hydrogen peroxide), bases, oxidizing agents, reducing agents, hydrophilic compounds, hydrophobic compounds (e.g., oils, fats, waxes), or mixtures thereof.

[0039]

[0043] FIG. 1C is a schematic partial cross-sectional side view of FIG. 1A showing an exemplary pad conditioning apparatus 112 combined with a polishing station 124. The cross-sectional view of FIG. 1C is taken at an angle different from that of FIG. 1B, for example, about 90 degrees apart. Each pad conditioning apparatus 112 includes an arm 113 that supports a conditioner head 115 on a respective platen 120. The arm 113 is rotatably fixed to a base 102. The distal end of the arm 113 is connected to a housing 116 of the conditioner head 115. A motor 117 is connected to the distal end of the arm 113 and rotates the conditioner head 115 during pad conditioning. The proximal end of the arm 113 is connected to a base 118 that extends upward from the base 102 of the housing 101. The base 118 is rotatable to pivot the arm 113 and laterally translate the conditioner head 115 across the polishing surface 131.

[0040]

[0044] Each polishing station 124 of the polishing apparatus 100 includes a station cup 146 that radially surrounds the platen 120. The station cup 146 has an inner side wall surface 147 that faces the platen 120. The inner side wall surface 147 extends above the polishing surface 131. The slurry 135 from the polishing pad 130 contacts the inner side wall surface 147 and collects inside the station cup 146. A drain 148 through the bottom and / or base 102 of the station cup 146 is used to discharge the slurry 135 collected in the station cup 146.

[0041]

[0045] During operation, accumulation of slurry 135 may occur on the inner surfaces of housing 101 due to accidental splashing, spraying, and / or aerosolization. For example, slurry 135 may accumulate on the surface of carrier head 126, on the surface of structures above carrier head 126 (e.g., overhead track 128, spray bar 134, sidewall 104, station cup 146, or pad conditioning device 112). To facilitate monitoring of the accumulation of slurry 135, one or more surfaces are at least partially covered with a fluorescent material. When a fluorescent material coating is used with a non-fluorescent slurry, the fluorescence intensity is inversely correlated with the slurry accumulation, such that a surface with a low fluorescence intensity or luminance corresponds to a higher level of slurry accumulation.

[0042]

[0046] One or more regions of interest on each surface may be covered with a fluorescent material. Alternatively, the entire surface may be covered with a fluorescent material. In some embodiments, the fluorescent material includes a fluorescent paint or a fluorescent tape. In some embodiments, the fluorescent material may fluoresce when exposed to ultraviolet radiation. The region of interest may correspond to a particular problem area. Alternatively, the region of interest may be an area that represents the slurry accumulation on the surface as a whole. In some embodiments, the fluorescent material is applied to regions of interest on a plurality of different surfaces.

[0043]

[0047] In some other embodiments, instead of using a fluorescent material coating, slurry 135 itself may include a fluorescent additive to facilitate monitoring of the slurry accumulation. In such embodiments, the fluorescence intensity is positively correlated with the slurry accumulation, such that a surface with a high fluorescence intensity or luminance corresponds to a higher level of slurry accumulation.

[0044]

[0048] To monitor the accumulation of slurry 135 on the surface, the polishing apparatus 100 includes at least one light source for illuminating the surface, at least one sensor for measuring the fluorescence intensity of the region of interest on the surface, and a processor for monitoring the slurry accumulation on the surface. In the illustrated embodiment, the polishing apparatus includes a plurality of cameras for illuminating and detecting the fluorescence intensity of a specific region of interest within the polishing apparatus 100. In FIGS. 1B-1C, the cameras are schematically shown. Each camera can be attached to a support (not shown) and / or directly or indirectly connected to respective components of the polishing apparatus 100. In some embodiments, each camera is fixed relative to the polishing apparatus 100. In some other embodiments, one or more cameras are movable relative to the polishing apparatus 100 to change the position and / or orientation of the camera and thus change its field of view. Further, each of the cameras is connected to a controller 190 (FIG. 1A) and is controlled by the controller 190.

[0045]

[0049] In some embodiments, the accumulation of slurry 135 can occur mainly on the upward-facing surface proximate to the platen 120. Thus, it may be desirable to position one or more of the plurality of cameras to view the surface adjacent to the platen 120 (e.g., the surface vertically above, vertically below, or radially surrounding the platen 120 in the vicinity) from above.

[0046]

[0050] In some embodiments, each camera includes a light source and an image sensor. Alternatively, the light source may be separated from the camera. For example, the light source may be a separate component of the polishing apparatus 100. In one example, the light source may include one or more light bars within the housing 101 of the polishing apparatus 100 to illuminate the processing region 105. In some embodiments, the light source is any ultraviolet light source. For example, the ultraviolet light source may be a source that emits ultraviolet radiation in the range of about 315 nm to about 400 nm, generally referred to as ultraviolet A radiation or invisible light. In some embodiments, the light source includes an array of light emitting diodes. In some embodiments, each camera uses a lens that can image an extended field of view, such as a wide-angle lens or a fish-eye lens. In some embodiments, each camera has a filter that matches the fluorescence wavelength range of the fluorescent material. In some embodiments, a single camera is configured to simultaneously image regions of interest on a plurality of different surfaces.

[0047]

[0051] The polishing apparatus 100 includes a camera 151 disposed above the carrier head 126. The camera 151 can be coupled to at least one of the overhead track 128 or the carriage 108 (shown in FIG. 1A). The position and orientation of the camera 151 enable imaging of the surface of the carrier head 126, such as the surface of the housing 129.

[0048]

[0052] The polishing apparatus 100 includes a camera 152 disposed above the polishing station 124. The camera 152 can be coupled to at least one of the upper wall 103 or the side wall 104. The position and orientation of the camera 152 enable imaging of the surface of the carrier head 126 or the surface of one or more structures above the carrier head 126 (e.g., the overhead track 128, the drive system 106, the drive shaft 107, or the carriage 108 (shown in FIG. 1A)).

[0049]

[0053] The polishing apparatus 100 includes a camera 153 disposed above the spray bar 134. The camera 153 can be connected to at least one of the upper wall 103, the side wall 104, the overhead track 128, the drive system 106, or the carriage 108 (shown in FIG. 1A). The position and orientation of the camera 153 enable imaging of the surface of the spray bar 134, such as the surface of the arm 136.

[0050]

[0054] The polishing apparatus 100 includes a camera 154 disposed in the processing area 105, for example, adjacent to the camera 152. The camera 154 can be connected to at least one of the upper wall 103, the side wall 104, the overhead track 128, the drive system 106, or the carriage 108 (shown in FIG. 1A). The position and orientation of the camera 154 enable imaging of the surface of the side wall 104.

[0051]

[0055] The polishing apparatus 100 includes a camera 155 disposed above the station cup 146. The camera 155 can be connected to at least one of the overhead track 128, the drive system 106, or the carriage 108 (shown in FIG. 1A). The position and orientation of the camera 155 enable imaging of the surface of the station cup 146, such as the inner side wall surface 147.

[0052]

[0056] The polishing apparatus 100 includes a camera 156 disposed above the pad conditioning device 112. The camera 156 can be connected to at least one of the upper wall 103, the side wall 104, the overhead track 128, the drive system 106, or the carriage 108 (shown in FIG. 1A). The position and orientation of the camera 156 enable imaging of the surface of the pad conditioning device 112, such as the surface of the arm 113, the conditioner head 115, or the motor 117.

[0053]

[0057] Figure 2 is a diagram showing a method 200 for monitoring slurry accumulation. Method 200 can be executed by a controller 190. In one embodiment, the controller 190 includes a non-transitory computer-readable medium storing instructions for executing method 200. In activity 202, the substrate 114 is polished within the polishing apparatus 100 using slurry 135. In particular, as shown in FIG. 1B, the slurry 135 is dispensed from the spray bar 134 onto the polishing surface 131 of the polishing pad 130. As described above, due to accidental splashing, spraying, and / or aerosolization, some slurry accumulation may occur on the inner surface of the housing 101. Usually, the accumulation of slurry is undetectable. However, as disclosed herein, one or more regions of interest on the inner surface of the polishing apparatus 100 are covered with a fluorescent material. Thus, slurry accumulation on the region of interest covers the fluorescent coating and reduces the measurable fluorescence intensity, or luminance, of the fluorescent material within the region of interest. FIG. 3 is a schematic diagram showing an exemplary setup 300 for monitoring slurry accumulation 301 on a surface 302. Referring to FIG. 3, the region of interest 304 is covered with a fluorescent material 306. When a portion of the fluorescent material 306 is covered by the slurry accumulation 301, the measurable fluorescence intensity of the region of interest 304 decreases.

[0054]

[0058] In activity 204, the light source 308 is switched on to illuminate the surface 302 including the region of interest 304. In some embodiments, the light source is switched on for a period of about 1 second or less than about 1 second (e.g., from about 1 millisecond to about 1 second, from about 1 millisecond to about 100 milliseconds, e.g., from about 1 millisecond to about 10 milliseconds). It may be desirable to limit the exposure time to reduce the potential for photo-corrosion of the substrate 114 or other sensitive materials within the housing 101 of the polishing apparatus 100. In some embodiments, as described in more detail below, when the light source 308 is switched on, auxiliary lighting such as normal indoor lighting in the factory can optionally be switched off to prevent interference with the fluorescence measurement.

[0055]

[0059] In Activity 206, when the region of interest 304 is illuminated, the fluorescence intensity of the region of interest is measured using a sensor such as image sensor 310. The fluorescence intensity may correspond to the amount of slurry accumulation 301 on the region of interest 304. In some embodiments, the sensor may be calibrated to work optimally with a particular type of fluorescent material and the illumination being implemented. In some embodiments, the sensor measurements may be normalized with respect to the fluorescence intensity of the fluorescent material in a clean state. In the illustrated embodiment using image sensor 310, measuring the fluorescence intensity includes capturing an image of the surface using image sensor 310. In one example, the light source 308 and the image sensor 310 are included in a camera such as one of the cameras 151-156 shown in FIGS. 1B and 1C. Although an image sensor is shown in the illustrated embodiment, any suitable fluorescence measurement sensor may be used.

[0056]

[0060] In some embodiments, the sensor measurements include data representing fluorescence outside the region of interest 304. For example, the image sensor 310 may capture an image of an area 312 that includes the region of interest 304 and an area surrounding the region of interest 314. In such embodiments, data processing is performed to select the region of interest 304 before determining the fluorescence intensity. For example, if the captured image includes an area surrounding the region of interest 314, the region of interest 304 can be selected by applying a computer algorithm to the image. It may be desirable to convert the fluorescence intensity of the region of interest 304 to a numerical value representing the slurry accumulation amount 301 in order to provide a practical indication of the slurry accumulation.

[0057]

[0061] In Activity 208, the fluorescence intensity is compared to a first range. The first range may include a lower limit of the fluorescence intensity in the region of interest, and if the intensity falls below this lower limit, the region of interest is considered to require cleaning. In other words, fluorescence intensity measured within the first range may be considered "clean", while fluorescence intensity measured outside the first range may be considered "dirty". For example, the lower limit of the first range may correspond to a threshold level of the thickness of the residue, the coverage of the residue, and / or the non-uniformity of the residue in the region of interest.

[0058]

[0062] In some embodiments, as described above, instead of or in addition to the overall fluorescence intensity, the non-uniformity of the residues within the region of interest can be monitored. The non-uniformity of the residues can be a parameter that is particularly useful for tracking after the polishing apparatus is returned online after cleaning. This is because changes in slurry accumulation can potentially be detected through measurements of fluorescence intensity non-uniformity before the same changes become apparent with respect to the overall fluorescence intensity. In other words, even before changes in the overall fluorescence intensity become detectable, as slurry accumulation occurs, the uniformity of the fluorescence intensity within the region of interest can be reduced by a detectable amount. In one embodiment, edge detection of discrete spots where slurry accumulation occurs can be used in conjunction with fluorescence intensity measurements to help monitor changes in non-uniformity.

[0059]

[0063] In activity 210, an alarm is generated when the fluorescence intensity is outside a first range or when threshold conditions associated with the first range are met. The alarm can include a user message indicating that cleaning is required. The alarm can specify a particular surface that needs to be cleaned, such as a surface corresponding to the region of interest identified as being outside the first range. The alarm may include a summary screen for presenting to the user one or more evaluations representing slurry accumulation on different surfaces of the polishing apparatus 100.

[0060]

[0064] In activity 212, based on the alarm, cleaning of the surface including the region of interest is scheduled and / or initiated. In some embodiments, the cleaning is performed while the polishing apparatus 100 remains online. For example, during polishing, components of the polishing apparatus 100, such as the carrier head 126 or the spray bar 134, can be intermittently rinsed or cleaned with deionized water or another suitable rinse fluid. Using the apparatus and / or method disclosed herein, rinsing can be scheduled and / or initiated based on the alarm. Further, using the apparatus and / or method disclosed herein, the rinse can be modified, such as by providing a longer rinse time or a specific spray recipe, for targeted cleaning of the surface including the region of interest corresponding to the alarm in activity 210.

[0061]

[0065] In some other embodiments, the polishing apparatus 100 is taken offline to perform preventive maintenance cleaning. For example, when the polishing apparatus 100 is offline, the components of the polishing apparatus 100 may be manually wiped. Using the apparatus and / or method disclosed herein, preventive maintenance cleaning can be scheduled based on an alarm. For example, at least the cleaning of the surface including the region of interest corresponding to the alarm in activity 210 can be automatically scheduled. Scheduling the cleaning of the tool only when necessary results in a more efficient cleaning schedule while shortening the tool downtime. Further, by cleaning only a specific region of the polishing apparatus 100, more efficient cleaning of the selected surface is achieved while shortening the tool downtime. Additionally, the cleaning process can be optimized by prioritizing the surfaces that need the most cleaning.

[0062]

[0066] The above description is directed to embodiments of the present disclosure, but other and further embodiments of the present disclosure may be devised without departing from the basic scope of the present disclosure, and the scope of the present disclosure is determined by the following claims.

Claims

1. A substrate polishing apparatus, a surface at least partially covered with a fluorescent material, a light source configured to illuminate the surface, an image sensor configured to image the surface, a processor coupled to the image sensor and configured to monitor slurry accumulation on the fluorescent material on the surface using data supplied from the image sensor and comprising a substrate polishing apparatus.

2. The substrate polishing apparatus according to claim 1, wherein the surface comprises at least a part of at least one of a carrier head, an overhead track, a spray bar, a side wall, a station cup, or a pad conditioning device.

3. The substrate polishing apparatus according to claim 1, wherein the fluorescent material comprises at least one of a fluorescent paint or a fluorescent tape.

4. The substrate polishing apparatus according to claim 1, wherein the light source comprises ultraviolet light.

5. The substrate polishing apparatus according to claim 1, wherein the light source and the image sensor are included in a camera using at least one of a wide-angle lens or a fish-eye lens configured to image an extended field of view.

6. The substrate polishing apparatus according to claim 1, wherein the image sensor comprises a filter adapted to the fluorescence wavelength range of the fluorescent material.

7. The substrate polishing apparatus according to claim 1, wherein the fluorescent material is applied to regions of interest on a plurality of different surfaces, and the image sensor comprises one or more cameras configured to simultaneously image each of the regions of interest.

8. The substrate polishing apparatus according to claim 1, wherein the processor comprises a non-transitory computer-readable medium storing instructions for a monitoring method, the monitoring method comprising: capturing an image of the surface including the fluorescent material; selecting a region of interest in the image; determining a fluorescence intensity of the region of interest, wherein the fluorescence intensity corresponds to an amount of slurry accumulation on the fluorescent material on the region of interest and including a substrate polishing apparatus according to claim 1.

9. A slurry accumulation monitoring method, comprising: capturing an image of a surface of a polishing apparatus, the surface being at least partially covered with a fluorescent material; selecting a region of interest in the image; determining a fluorescence parameter of the region of interest, wherein a value of the fluorescence parameter corresponds to an amount of slurry accumulation on the fluorescent material on the region of interest and including a method.

10. The method according to claim 9, wherein the fluorescence parameter includes at least one of fluorescence intensity or non-uniformity of fluorescence intensity.

11. The method according to claim 9, further comprising illuminating the surface with a light source during capture of the image.

12. The method according to claim 9, wherein selecting the region of interest includes applying a computer algorithm to the image.

13. The method according to claim 9, wherein the region of interest corresponds to a portion of the surface covered with the fluorescent material.

14. comparing the value of the fluorescence parameter with a first range; generating an alarm when the value of the fluorescence parameter meets a threshold condition associated with the first range The method according to claim 9, further comprising.

15. The method according to claim 14, further comprising at least one of scheduling or initiating cleaning of the surface including the region of interest based on the alarm.

16. A substrate polishing apparatus, comprising: a surface at least partially covered with a fluorescent material; a light source configured to illuminate the surface; a sensor configured to measure the fluorescence intensity of a region of interest on the surface; a non-transitory computer-readable medium storing instructions for a monitoring method; and wherein the monitoring method includes: polishing a substrate in the substrate polishing apparatus with a slurry, wherein slurry accumulation on the surface reduces the measurable fluorescence intensity of the region of interest; switching on the light source; using the sensor to measure the fluorescence intensity of the region of interest when the light source is switched on; comparing the measured fluorescence intensity with a first range; and generating an alarm when the measured fluorescence intensity is outside the first range. A substrate polishing apparatus.

17. The substrate polishing apparatus according to claim 16, wherein the fluorescent material includes at least one of a fluorescent paint or a fluorescent tape, and the light source includes ultraviolet light.

18. The substrate polishing apparatus according to claim 16, wherein the sensor includes an image sensor, and the monitoring method further includes capturing an image of the surface using the image sensor.

19. The substrate polishing apparatus according to claim 18, wherein the monitoring method further includes selecting a region of interest in the image corresponding to a portion of the surface covered with the fluorescent material.

20. The substrate polishing apparatus according to claim 16, wherein the monitoring method further includes at least one of scheduling or starting the cleaning of the surface including the region of interest based on the alarm.

21. The processor includes a non-transitory computer-readable medium storing instructions for a monitoring method, and the monitoring method includes capturing an image of the surface including the fluorescent material, selecting a region of interest in the image, determining a non-uniformity of the fluorescence intensity in the region of interest, wherein the non-uniformity of the fluorescence intensity corresponds to a change in slurry accumulation on the region of interest. The substrate polishing apparatus according to any one of claims 1 to 7.

22. The method according to any one of claims 9 and 11 to 15, wherein the fluorescence parameter includes a non-uniformity of fluorescence intensity, and the non-uniformity of the fluorescence intensity corresponds to a change in slurry accumulation.

23. The substrate polishing apparatus according to any one of claims 16 to 20, wherein the measured value of the fluorescence intensity further includes a non-uniformity of the fluorescence intensity.

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