Patent Publication Number: US-2023150084-A1

Title: Wafer surface chemical distribution sensing system and methods for operating the same

Description:
FIELD 
     The present disclosure relates generally to the field of semiconductor manufacturing, and specifically to a wafer surface chemical distribution sensing system and methods for operating the same. 
     BACKGROUND 
     Chemical mechanical polishing (CMP) is a process that forms smooth and planarized surfaces by removing protruding portions of a structure having topographic height variations. CMP is employed during semiconductor manufacturing to planarize top surfaces of patterned structures of semiconductor devices. 
     SUMMARY 
     According to another aspect of the present disclosure, a chemical mechanical polishing (CMP) includes a polishing apparatus configured to polish a wafer by performing a chemical mechanical polishing (CMP) process thereupon; and a roll cleaning apparatus configured clean the wafer after performing the CMP process thereupon. The roll cleaning apparatus comprises a rotating roll brush configured to roll against a surface of the wafer during operation, a fluid supply system configured to apply a fluid on the surface of the wafer, and an array of liquid sensors configured to detect a distribution of the fluid on the surface of the wafer. 
     According to another aspect of the present disclosure, a method includes performing a chemical mechanical polishing (CMP) process on a wafer in a CMP apparatus, loading the wafer into a roll cleaning apparatus after performing the CMP process on the wafer, applying a fluid on a surface of the wafer, brushing the surface of the wafer with rotating roll brush, and measuring a distribution of the fluid on the surface of the wafer while brushing the surface of the wafer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a to schematic view of an exemplary chemical mechanical polishing system according to an embodiment of the present disclosure. 
         FIG.  2    is a schematic perspective view of a chemical mechanical polishing apparatus according to an embodiment of the present disclosure. 
         FIG.  3 A  is a schematic vertical cross-sectional view of a first exemplary roll cleaning apparatus according to an embodiment of the present disclosure. 
         FIG.  3 B  is a schematic perspective view of the brush region of the first exemplary roll cleaning apparatus of  FIG.  3 A  according to an embodiment of the present disclosure 
         FIG.  4    is a schematic vertical cross-sectional view of a second exemplary roll cleaning apparatus according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     As discussed above, the embodiments of the present disclosure are directed to a wafer surface chemical distribution sensing system and methods for operating the same, the various aspects of which are described below. 
     A roll brush unit may be employed in a chemical mechanical polishing (CMP) system to provide a wafer cleaning process after a chemical mechanical polishing process. The wafer surface has a high density of dust and byproduct particles after the polishing process. Insufficient removal of the dust and the byproduct particles from the wafer surface can cause various types of failure within the metal interconnect structures or semiconductor devices located on the wafer. Thus, contamination in a roll brush unit may result in an increase in defects within the wafer. 
     Generally, uniform chemical distribution (e.g., distribution of a fluid including cleaning chemical(s)) within a roll brush unit is desired in performing an effective and uniform roll cleaning process. According to an aspect of the present disclosure, chemical distribution within a roll brush unit over a surface of a wafer can be controlled based on measurement of fluid thickness, shape and/or volume distribution over a surface of a wafer and adjustment of the flow rate and/or the application location of the cleaning fluid including the cleaning chemical. A sensing system for measuring local thicknesses, shape and/or volume of a cleaning fluid is employed to measure a two-dimensional distributional thickness distribution of the cleaning fluid. 
     Referring to  FIG.  1   , an exemplary chemical mechanical polishing (CMP) system  10  according to an embodiment of the present disclosure is illustrated in a plan view. The exemplary CMP system  10  may comprise a cluster tool which comprises a loading/unloading unit  1000 , a CMP apparatus  2000 , and a wafer cleaning apparatus  3000  include a set of cleaning chambers. The set of cleaning chambers may comprise, for example, a first cleaning chamber  3100 , a second cleaning chamber  3200 , a third cleaning chamber  3300 , optional additional cleaning chambers (not shown), and a drying chamber  3400 . 
     The loading/unloading unit  1000  is configured to mount at least one open cassette, at least one SMIF (Standard Manufacturing Interface) pod, and/or at least one FOUP (Front Opening Unified Pod). Each cassette, each SMIF pod, and/or each FOUP are configured to hold a plurality of wafers (e.g., silicon wafers), such as 25-30 wafers. The SMIF and the FOUP are an airtight container that can house a wafer cassette, and can be sealed to provide an airtight environment to wafers located within the wafer cassette. At least one transfer robot (not shown) can be provided within the loading/unloading unit  1000  and/or within the CMP apparatus  2000  to transport wafers from the loading/unloading unit  1000  to the CMP apparatus  2000 . The loading/unloading unit  1000  may comprise a chamber of the cluster tool (i.e., of the system  10 ). The chamber may have walls and openings (e.g., load locks) to the CMP apparatus  2000  and the drying chamber  3400 . 
     Referring to  FIG.  2   , the CMP apparatus  2000  within the exemplary CMP system  10  is illustrated. The CMP apparatus  2000  may comprise another chamber of the cluster tool (i.e., of the system  10 ). The chamber may have walls and openings (e.g., load locks) to the loading/unloading unit  1000  and the first cleaning chamber  3100 . 
     The CMP apparatus  2000  includes a polishing pad  112  located on a top surface of a platen  110 , a wafer carrier  140  that is configured to hold a work piece (such as a wafer  41 ) upside down, a slurry dispenser  120  that is configured to dispense slurry  122  over the top surface of the polishing pad  112 , and a pad conditioning unit ( 130 ,  132 ) that can be used to condition the top surface of the polishing pad  112 . 
     The platen  110  can have a generally cylindrical shape, and can have a circular top surface that can be large enough to accommodate the polishing pad  112 . The polishing pad  112  can have a generally circular horizontal-cross-sectional shape with a diameter that is at least twice the diameter of the wafer  41 . For example, in embodiments in which the diameter of the wafer  41  is 300 mm, the diameter of the polishing pad  112  can be at least 600 mm. In embodiments in which the diameter of the wafer  41  is 450 mm, the diameter of the polishing pad  112  can be at least 900 mm. Generally, the ratio of the diameter of the polishing pad  112  to the diameter of the wafer  41  can be in a range from 2 to 6, such as from 2.5 to 4, although greater or lesser ratios can be used. The polishing pad  112  can include a textured top surface that is employed as a polishing surface during a polishing operation. The polishing pad  112  of the embodiments of the present disclosure includes debris  124  extraction tunnels connected to perforation holes in an upper polishing pad layer. Methods for manufacturing the polishing pad  112  of the present disclosure, and the structural features of the polishing pad  112  are described below in more detail with accompanying drawings. 
     The platen  110  can be configured to rotate around a vertical axis (VA) passing through the geometrical center of the platen  110 . For example, a platen motor assembly  108  can be provided underneath the platen  110 , and can rotate the platen  110  around the vertical axis (VA) passing through the geometrical center of the platen  110 . As used herein, a geometrical center of an object refers to a center of mass of a hypothetical object occupying the same volume as the object and having a uniform density throughout. If an object has a uniform density, the geometrical center coincides with the center of gravity. The platen  110  can be configured to provide a rotational speed in a range from 10 revolutions per minute to 240 revolutions per minute, although faster or slower rotational speed can be used. 
     The wafer carrier  140  can be configured to hold the wafer  41  on a bottom surface thereof. Thus, the wafer carrier  140  can press the wafer  41  onto the top surface of the polishing pad  112 . In one embodiment, the wafer carrier  140  can include a vacuum chuck configured to provide suction to the backside of the wafer  41 . In one embodiment, differential suction pressures can be applied across different backside areas of the wafer  41 . For example, the suction pressure applied to the center portion of the wafer  41  can be different from the suction pressure applied to the peripheral portion of the wafer  41  to provide uniform polishing rate across the entire area of the front side of the wafer  41  that contacts the polishing pad  112 . In one embodiment, the wafer carrier  140  can include a retaining ring having an annular shape and configured to hold the wafer  41  therein so that the wafer  41  does not slide out from underneath the wafer carrier  140 . 
     A polishing head  142  can be provided over the wafer carrier  140 . The polishing head  142  can include a rotation mechanism that provides rotation to the wafer carrier  140 . In some embodiments, a gimbal mechanism can be provided between the rotation mechanism and the wafer carrier  140  so that the wafer carrier  140  tilts in a manner that provides maximum physical contact between the entire front surface of the wafer  41  and the polishing pad  112 . The combination of the polishing head  142  and the wafer carrier  140  constitutes a wafer polishing unit ( 140 ,  142 ) that positions and rotates the wafer  41  in a manner that induces polishing of material portions on the front side of the wafer  41  through abrasion caused by sliding contact with the top surface of the polishing pad  112 . 
     In one embodiment, the wafer  41  and the wafer carrier  140  can rotate around the vertical axis (not illustrated) passing through the geometrical center of the wafer carrier  140 . A polishing pivot pillar structure  144  can be affixed to a frame (not shown) of the CMP apparatus such that the polishing pivot pillar structure  144  can rotate around a vertical axis (not illustrated) passing through the geometrical center of the polishing pivot pillar structure  144 . The vertical axis passing through the geometrical center of the polishing pivot pillar structure  144  can be stationary relative to the frame of the CMP apparatus. 
     A polishing arm  146  mechanically connects the polishing head  142  to the polishing pivot pillar structure  144 . Thus, upon rotation of the polishing pivot pillar structure  144  around the vertical axis passing through the geometrical center of the polishing pivot pillar structure  144 , the polishing arm  146  can rotate around the vertical axis passing through the geometrical center of the polishing pivot pillar structure  144 . The polishing head  142  can move around the vertical axis passing through the geometrical center of the polishing pivot pillar structure  144  over the polishing pad  112 . Lateral movement of the wafer polishing unit ( 140 ,  142 ) over the polishing pad  112  can enhance uniformity of polish rate across the wafer  41  during the CMP process. 
     The slurry dispenser  120  can be configured to dispense the slurry  122  over the top surface of the polishing pad  112 . The slurry  122  can include any slurry known in the art, such as commercially available slurries for chemical mechanical polishing processes. 
     The pad conditioning unit ( 130 ,  132 ) can be used to precondition the polishing pad  112  prior to and/or during the CMP process that is used to polish material portions from the front surface of the wafer  41  that contacts the top surface of the polishing pad  112 . In one embodiment, the pad conditioning unit ( 130 ,  132 ) can include a pad conditioning disk  130  and a conditioning head  132  that is configured to hold the pad conditioning disk  130 . The pad conditioning disk  130  includes an abrasive bottom surface that can precondition the top surface of the polishing pad  112 . Typically, the abrasive bottom surface of the pad conditioning disk  130  embeds abrasive particles, such as diamond particles. The pad conditioning disk  130  can be attached to the conditioning head  132  in a manner that provides rotation of the pad conditioning disk around a vertical axis (not shown) passing through the geometrical center of the pad conditioning disk  130  without falling out from the conditioning head  132 . 
     A conditioner pivot pillar structure  134  can be affixed to a frame (not shown) of the CMP apparatus such that the conditioner pivot pillar structure  134  can rotate around a vertical axis (not shown) passing through the geometrical center of the conditioner pivot pillar structure  134 . The vertical axis passing through the geometrical center of the conditioner pivot pillar structure  134  can be stationary relative to the frame of the CMP apparatus. 
     A pad conditioner arm  136  mechanically connects the conditioning head  132  to the conditioner pivot pillar structure  134 . A pad conditioner arm  136  mechanically connects the conditioning head  132  to the conditioner pivot pillar structure  134 . Thus, upon rotation of the conditioner pivot pillar structure  134  around the vertical axis passing through the geometrical center of the conditioner pivot pillar structure  134 , the pad conditioner arm  136  can rotate around the vertical axis passing through the geometrical center of the conditioner pivot pillar structure  134 . The conditioning head  132  can move around the vertical axis passing through the geometrical center of the conditioner pivot pillar structure  134  over the polishing pad  112 . Lateral movement of the pad conditioning unit ( 130 ,  132 ) over the polishing pad  112  can enhance uniformity of the surface condition of the polishing pad  112  after the pad pre-conditioning process. 
     The CMP apparatus  2000  of the embodiments of the present disclosure can include a process controller  200  electrically connected (e.g., via wired and/or wireless connections) to electrical components that control movement of various mechanical parts of the CMP apparatus. For example, the process controller  200  can be electrically connected to, and can be configured to control operation of, each of the platen motor assembly  108 , the polishing pivot pillar structure  144 , the wafer polishing unit ( 140 ,  142 ), the conditioner pivot pillar structure  134 , the pad conditioning unit ( 130 ,  132 ), and the slurry dispenser  120 . For example, the process controller  200  can control the rotational speed of the platen  110 , the polishing pivot pillar structure  144 , the wafer carrier  140 , the conditioner pivot pillar structure  134 , and the pad conditioning disk  130 , and can control the location of the slurry dispensation point and the rate of slurry dispensation. 
     Generally, the CMP apparatus  2000  according to various embodiments can include a polishing pad  112  located on a top surface of a platen  110  configured to rotate around a vertical axis VA passing through the platen  110 , a wafer carrier  140  that holds a wafer  41  and facing the polishing pad  112 , a slurry dispenser  120  configured to dispense slurry  122  over the polishing pad  112 , and a process controller  200  configured to control operation of components within the wafer carrier  140  and other components of the CMP apparatus. For example, the process controller  200  may control the rotation speed of the platen  110 , the rotation speed of the wafer carrier  140 , and/or the downforce that the wafer carrier  140  applies to the polishing pad  112 . The CMP apparatus may include an assembly of a conditioning head  132  and a pad conditioning disk  130  that is configured to condition the top surface of the polishing pad  112 . 
     Referring back to  FIG.  1   , the CMP apparatus  2000  and/or the wafer cleaning apparatus  3000  may comprise additional transfer robots configured to transfer wafers from the CMP apparatus  2000  into the wafer cleaning apparatus  3000  and/or between the various cleaning chambers within the wafer cleaning apparatus  3000 . The wafers are transferred via openings (e.g., load locks) between the chambers. 
     The first cleaning chamber  3100 , the second cleaning chamber  3200 , the third cleaning chamber  3300 , and/or the additional cleaning chambers (not shown) may comprise various types of cleaning chambers, which may include, for example, a roll cleaning apparatus, a pen cleaning chamber, a buff processing chamber, a megasonic cleaning chamber, and/or additional types of processing chambers. The order of the various types of cleaning chambers may be selected to provide effective cleaning to each wafer. Generally, large particles are removed first and fine particles are removed at later cleaning processes. Each wafer can be transferred into the drying chamber  3400  after performing all cleaning processes, and upon drying, can be transferred to the loading/unloading unit  1000  by a transfer robot. 
     According to an aspect of the present disclosure, at least one of the cleaning chambers, such as at least one of the first cleaning chamber  3100 , the second cleaning chamber  3200 , or the third cleaning chamber  3300 , comprises a roll cleaning apparatus.  FIG.  3 A  is a schematic vertical cross-sectional view of a first exemplary roll cleaning apparatus  300 A according to an embodiment of the present disclosure.  FIG.  4    is a schematic vertical cross-sectional view of a second exemplary roll cleaning apparatus  300 B according to another embodiment of the present disclosure. The apparatus  300 A or  300 B may be located in one of the first cleaning chamber  3100 , the second cleaning chamber  3200 , or the third cleaning chamber  3300 . 
     Referring collectively to  FIGS.  3 A,  3 B and  4   , a roll cleaning apparatus ( 300 A or  300 B) of the embodiments of the present disclosure can include a fluid supply system  310  configured to apply a fluid  320  on the surface of the wafer  41 , a rotating roll brush  330  configured to roll against a surface of a wafer  41  during operation, and an array of liquid sensors ( 360  or  460 ) configured to detect a two-dimensional and/or a three-dimensional distribution of the fluid  320  on the surface of the wafer  41  in areas that are not covered by the rotating roll brush  330 . 
     In one embodiment, the fluid supply system  310  comprises a fluid storage container  312  (e.g., cleaning chemical tank or barrel) that is fluidly connected (e.g., via a tube, pipe or another conduit) to at least one nozzle  314  configured to spray the fluid  320  onto the surface of the wafer  41 . As shown in  FIG.  3 B , the first rotating roll brush  330  is configured to roll against the front surface of a wafer  41 . In one embodiment, the roll cleaning apparatus ( 300 A or  300 B) further comprises a second rotating roll brush  332  configured to roll against a back surface of the wafer  41  during the cleaning operation. The brushes ( 330 ,  332 ) roll in opposite directions from each other, as shown in  FIG.  3 B . Furthermore, the wafer  41  may also rotate between the brushes ( 330 ,  332 ) during the cleaning operation. 
     Generally, the rotating roll brushes ( 330 ,  332 ) comprise a material having a Young&#39;s modulus that is less than 1% of a Young&#39;s modulus of silicon oxide (which is about 35 GPa). For example, the rotating roll brushes ( 330 ,  332 ) may comprise a polymer material or resin, such as polyvinylchloride (PVC). 
     In one embodiment, the array of liquid sensors comprises an array of ultrasonic sensors ( 360  or  460 ). In one embodiment, each of the ultrasonic sensors ( 360  or  460 ) can be configured to measure a local thickness of the fluid at a respective measurement location based on a measured intensity of an ultrasound wave  374  (i.e., a reflected ultrasound wave) from the respective measurement location. Each measurement location can be located on the top surface of the wafer  41 . The shape and/or volume of the fluid may be calculated by the controller  200  based on the fluid thickness measurements at different locations on the top surface of the wafer  41 . In one embodiment, each of the ultrasonic sensors ( 360  or  460 ) comprises a respective directional ultrasonic sensor that increases attenuation of an incident ultrasonic wave as a function of an angle between a sensor alignment direction of a respective ultrasonic sensor ( 360  or  460 ) and an incidence direction of the incident ultrasonic wave. The sensor alignment direction is the direction connecting the respective ultrasonic sensor ( 360  or  460 ) and the respective measurement location. In one embodiment, the sensor alignment direction may be a downward vertical direction, or a downward direction with a taper angle in a range from 0 degree to 30 degrees with respective to a vertical direction. In one embodiment, the sensitivity of the ultrasonic sensors ( 360  or  460 ) may be highly directional. In an illustrative example, the sensitivity of the ultrasonic sensors ( 360  or  460 ) may decrease by a factor of 2˜4 decibels per degree in angular offset from the direction of the maximum sensitivity up to an angular offset of about 10 degrees. 
     In an embodiment illustrated in  FIG.  3 A , the roll cleaning apparatus  300 A comprises an array of integrated ultrasound emitter-sensor assemblies  360 . Each of the integrated ultrasound emitter-sensor assemblies  360  comprises a combination of an ultrasound emitter and an ultrasonic sensor that is a component (i.e., an element) of the array of ultrasonic sensors. In this case, the array of ultrasonic sensors comprises components of the array of integrated ultrasound emitter-sensor assemblies  360 . 
     In one embodiment, each of the ultrasonic emitters in the array of integrated ultrasound emitter-sensor assemblies  360  may be configured to emit a respective directed ultrasonic wave at a respective measurement location. In one embodiment, each of the integrated ultrasound emitter-sensor assemblies  360  may be configured to determine, and to output, a ratio of a magnitude of a detected ultrasound wave  374  from a respective ultrasonic sensor (i.e., the ultrasonic sensor of the integrated ultrasound emitter-sensor assembly  360 ) to a magnitude of an emitted ultrasound wave  372  from a respective ultrasound emitter (i.e., the ultrasound emitter of the integrated ultrasound emitter-sensor assembly  360 ). 
     In one embodiment, each of the integrated ultrasound emitter-sensor assemblies  360  may be calibrated prior to operation so that the output is proportional to the ratio of the magnitude of the detected ultrasound wave  374  as detected by the ultrasonic sensor to the magnitude of the emitted ultrasound wave  372  from the ultrasound emitter. Generally, the greater the thickness of the fluid  320  at a measurement location, the lower the ratio of the magnitude of the detected ultrasound wave  374  as detected by a ultrasonic sensor to the magnitude of the emitted ultrasound wave  372  from a ultrasound emitter within a same integrated ultrasound emitter-sensor assembly  360 . 
     In one embodiment, each of the ultrasonic emitters in the array of the integrated ultrasound emitter-sensor assemblies  360  may be configured to sequentially emit ultrasound waves at multiple frequencies. The emission frequencies of the ultrasonic emitters may be greater than 20 kHz and/or 30 kHz and/or 50 kHz, and may be less than 10 MHz and/or 1 MHz and/or 100 kHz. 
     In an embodiment illustrated in  FIG.  4   , the roll cleaning apparatus  300 B comprises an array of ultrasonic sensors  460  that are not integrated with ultrasound emitters  400 . In this case, the roll cleaning apparatus  300 B comprises at least one ultrasound emitter  440  configured to emit an ultrasound wave  372  toward the surface of the wafer  41 . The at least one ultrasound emitter  440  can be located at different locations than the array of ultrasonic sensors  460 . 
     In one embodiment, each ultrasonic emitter  440  may be configured to sequentially emit ultrasound waves at multiple frequencies. The emission frequencies of the ultrasonic emitters  440  may be greater than 20 kHz and/or 30 kHz and/or 50 kHz, and may be less than 10 MHz and/or 1 MHz and/or 100 kHz. 
     Generally, the operation of the various components of the roll cleaning apparatus ( 300 A or  300 B) can be controlled by the process controller  200 . For example, the output from the array of ultrasonic sensors ( 360 ,  460 ) can be transmitted to the process controller, and a map of the two-dimensional distribution of the thickness of the fluid  320  can be generated by the process controller  200  employing a model-based calculation. In this case, a thickness distribution model that correlates the outputs from the array of ultrasonic sensors ( 360 ,  460 ) to a two-dimensional thickness distribution of the fluid  320  may be employed to generate the map of the two-dimensional distribution of the thickness of the fluid  320 . Furthermore, the three-dimensional volume and/or shape distribution may also be calculated by the process controller  200  from the two-dimensional distribution of the thickness of the fluid  320 . The flow rate of the fluid  320  out of the nozzle  314  and/or the application direction of the nozzle  314  can be adjusted by the process controller  200  based on the chemical distribution (e.g., based on calculated map of the two-dimensional distribution of the thickness of the fluid  320 , etc.) to provide a more uniform roll clean process. 
     Referring to all drawings and according to various embodiments of the present disclosure, a method of operating a chemical mechanical polishing (CMP) system is provided. A CMP process can be performed on a wafer  41  in the CMP apparatus  2000 . The wafer  41  is then loaded into the roll cleaning apparatus ( 300 A or  300 B) after performing the CMP process on the wafer  41 . A fluid  320  can be applied onto a surface of the wafer  41 . The surface of the wafer  41  is brushed with a rotating roll brush  330 . The distribution of the fluid  320  on the surface of the wafer  41  is measured while brushing the surface of the wafer  41 . 
     In one embodiment, the fluid  320  comprises a chemical cleaning fluid which is applied to the surface of the wafer  41  through a nozzle  314 , and the flow rate of the fluid  320  through the nozzle  314  can be adjusted based on the measured distribution of the fluid  320  to provide substantially uniform thickness distribution for the fluid  320  over the wafer  41 . In one embodiment, the direction of the nozzle  314  may be adjusted based on the measured distribution of the fluid  320 . Alternatively, or in addition, the brush ( 330 ,  332 ) rotation speed and/or the wafer  41  rotation speed may also be adjusted based on the measured distribution of the fluid  320 . 
     In one embodiment, the distribution of the fluid  320  can be measured by measuring a thickness distribution of the fluid  320  on the surface of the wafer  41  in areas that are not covered by the rotating roll brush  330 . 
     In one embodiment, the distribution of the fluid  320  is measured ultrasonically. In one embodiment, the roll cleaning apparatus  300 A of  FIG.  3 A  comprises an array of integrated ultrasound emitter-sensor assemblies  360 . Each of the integrated ultrasound emitter-sensor assemblies  360  comprises a combination of an ultrasound emitter and an ultrasonic sensor. In another embodiment, the roll cleaning apparatus  300 B of  FIG.  4    comprises at least one ultrasound emitter  440  which emits an ultrasound wave  372  toward the surface of the wafer and an array of ultrasonic sensors  460  which ultrasonically measure the distribution of the fluid  320 . 
     Embodiments of the present disclosure provide methods for detecting the distribution of the cleaning chemical fluid on a surface of a wafer  41 . The distribution can include the thickness of the fluid  320 , the shape of the fluid  320 , the volume of the fluid  320 , and/or other spatial distribution of the fluid  320 , etc. The array of liquid sensors can output the measurement data as synthesized images or as numerical data. In an illustrative example, in case insufficient amount of fluid  320  on the surface of the wafer  41  is detected at wafer edge regions, at least one nozzle  314  can be repositioned, or the flow rate of the fluid  320  through at least one nozzle  314  can be increased, so that the amount of the fluid  320  at the wafer edge region can be increased. 
     Continuous monitoring of the distribution of the fluid  320  can be performed so that application of the fluid  320  from the nozzle(s)  314  can be continuously adjusted throughout the roll clean process. The apparatuses and the methods of the embodiments of present disclosure may be employed to continuously monitor and adjust the fluid distribution on the surface of the wafer  41  in real time to improve the post CMP wafer cleaning process. 
     Although the foregoing refers to particular preferred embodiments, it will be understood that the disclosure is not so limited. It will occur to those of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the disclosure. Where an embodiment employing a particular structure and/or configuration is illustrated in the present disclosure, it is understood that the present disclosure may be practiced with any other compatible structures and/or configurations that are functionally equivalent provided that such substitutions are not explicitly forbidden or otherwise known to be impossible to one of ordinary skill in the art. All of the publications, patent applications and patents cited herein are incorporated herein by reference in their entirety.