Patent Publication Number: US-2020298371-A1

Title: Slurry dispersion system with real time control

Description:
RELATED APPLICATIONS 
     The present application is a continuation application of U.S. application Ser. No. 14/502,917, filed on Sep. 30, 2014, now U.S. Pat. No. 10,688,623, issued Jun. 23, 2020 which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     In semiconductor fabrication, a chemical mechanical polishing (CMP) technique is usually used for removing excess materials formed on a semiconductor substrate and for global planarization of layers formed on the semiconductor substrate. In a CMP process, a slurry is used for both chemical and mechanical polishing, which includes chemicals and abrasive particles. Typically, the slurry is provided by a slurry dispersion system (SDS) and applied directly onto a wafer surface to be polished. The quality of the slurry affects the performance of the CMP process, such as process defects and a removal rate. If the quality of the slurry is found abnormal, the slurry dispersion system may be adjusted or stopped in order to avoid causing damages to the wafer surface in the CMP process. 
     Conventionally, the quality of the slurry stored in the slurry dispersion system is analyzed by an off-line monitor, but not in real time. In other words, the abnormality of the slurry cannot be detected in time, and may cause damages to the wafer surface during the CMP process before being detected by the off-line monitor, thus resulting in performance degradation of the CMP process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a schematic diagram of a slurry dispersion system in accordance with various embodiments. 
         FIG. 2  is flow chart of a method for controlling slurry quality of a slurry dispersion system in accordance with some embodiments. 
         FIG. 3  is a schematic diagram of a slurry dispersion system in accordance with various embodiments. 
         FIG. 4  is flow chart of a method for controlling slurry quality of a slurry dispersion system in accordance with some embodiments. 
         FIG. 5  is a schematic diagram of a slurry dispersion system in accordance with various embodiments. 
         FIG. 6  is a flow chart of a method for real time feed-back controlling a slurry dispersion system in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     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 present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Terms used herein are only used to describe the specific embodiments, which are not used to limit the claims appended herewith. For example, unless limited otherwise, the term “a”, “an” or “the” of the single form may also represent the plural form. 
     The terms such as “first,” “second” and “third” are used for describing various layers, though such terms are only used for distinguishing one layer from another layer. Therefore, the first layer may also be referred to as the second layer without departing from the spirit of the claimed subject matter, and the others are deduced by analogy. 
     Embodiments of the present disclosure are directed to providing a slurry dispersion system and a method for real time feed-back controlling the slurry dispersion system used for a chemical mechanical polishing (CMP) process. In this method, a slurry in the slurry dispersion system is first sampled to obtain a sampled slurry, and then, a parameter of the sampled slurry is measured, and factors of the slurry dispersion system are controlled based on the parameter. In the embodiments of the present disclosure, the parameter of the sampled slurry is measured in real-time, and the quantity of large particles in the slurry is automatically controlled, and the quality of the slurry is compensated or adjusted instantly. Therefore, automatic and dynamic control of the slurry dispersion system is realized, so as to enhance supplying quality and stability of the slurry dispersion system, and thus process defects and a removal rate of the CMP process can be improved. 
       FIG. 1  is schematic diagram of a slurry dispersion system  100  in accordance with some embodiments. The slurry dispersion system  100  is utilized for providing a slurry to a polishing process such as CMP process or the like. In the present disclosure, the slurry dispersion system  100  is applied to a CMP tool which performs a CMP process, in which the slurry includes abrasive particles for abrasively removing a portion of a workpiece surface (such as a wafer surface). The abrasive particles of the slurry may include, but not limited to, ceria, silica and/or alumina. As shown in  FIG. 1 , the slurry dispersion system  100  includes a slurry source system  110 , a reactor  120 , a slurry supply system  130  and a control system  140 . The slurry source system  110  includes a slurry drum  111 , a slurry pump  112 , a source tank  113 , a filter  114  and a three-way valve  115 . The slurry drum  111  contains an undiluted slurry. The slurry pump  112  transports the undiluted slurry to the source tank  113 . The slurry pump  112  may control the transport rate of the slurry undiluted to the source tank  113 . In the source tank  113 , the undiluted slurry is collected from the slurry drum  111  and re-circuited through the filter  114  and the three-way valve  115  via a pump  113 A. The filter  114  receives the undiluted slurry from the source tank  113 , and selectively filters the undiluted slurry. The abrasive particles of the undiluted slurry have various sizes, in which an abrasive particle is defined as a large particle if its size is greater than a predetermined size. It is noted that the predetermined size for determining the large particle may vary in accordance with various applications. The filter  114  filters out at least a portion of the large particles in the undiluted slurry, such that a large particle count (LPC) value of the undiluted slurry is decreased. The three-way valve  115  controls the undiluted slurry to stay in the same stage or to enter the next stage. That is, the three-way valve  115  controls the undiluted slurry to flow back to the source tank  113  or into the reactor  120 . The source tank  113 , the filter  114  and the three-way valve  115  form a re-circulation loop, so as to dynamically adjust the LPC value of the undiluted slurry in the source tank  113 . 
     In the reactor  120 , the undiluted slurry from the slurry source system  110  is mixed with at least one chemical to obtain a mixed slurry. The chemical may include, but not limited to, hydrogen peroxide, potassium and/or ammonium hydroxide. In some embodiments, the reactor  120  is a static mixer used to mix the slurry with the chemical to form the mixed slurry. In some embodiments, the reactor  120  is a mixing tank. 
     The slurry supply system  130  includes a supply tank  131  and a filter  132 . In the supply tank  131 , the mixed slurry is collected from the reactor  120 , and is re-circulated through the filter  132  via a pump  131 A. The filter  132  receives the mixer slurry from the supply tank  131 , and selectively filters the mixed slurry. The filter  132  filters out at least a portion of the large particles of the mixed slurry, such that the number of large particles of the mixed slurry is decreased. The supply tank  131  and the filter  132  form a re-circulation loop, so as to dynamically adjust the number of large particles of the mixed slurry in the supply tank  131 . A pump  131 B is used for transporting the mixed slurry to the CMP tool. The mixed slurry may return to the supply tank  131  from the CMP tool. 
     The control system  140  includes a sampling valve  141 , an in-line analyzer  142  and a controller  143 . The sampling valve  141  samples the undiluted slurry outputted from the source tank  113  to obtain a sampled slurry. The in-line analyzer  142  measures at least one parameter of the sampled slurry. The parameter may include a large particle count (LPC) value, which is a value relative to the number of large particles of the slurry, and/or include a zeta potential value, which is a value relative to the average electrical potential at a hydrodynamic slipping plane adjacent to a solid surface of each large particle exposed to a dispersing medium of the slurry. The in-line analyzer  142  generates an indication signal based on the parameter, in which the indication signal indicates at least one characteristic of the slurry. The controller  143  receives the indication signal, and generates a control signal based on the indication signal to perform a real time feedback control on the slurry dispersion system  100 . 
       FIG. 2  is flowchart diagram of a method  200  for controlling slurry quality of a slurry dispersion system in accordance with various embodiments. The method  200  may be operated in the slurry dispersion system  100  or other systems similar to the slurry dispersion system  100 . The following describes the method  200  operated in the control system  140  of the of the slurry dispersion system  100  for illustration. The method  200  begins at operation  202 , where the sampling valve  141  samples the slurry outputted from the source tank  113 , and allows the sampled slurry to be forwarded to the in-line analyzer  142 . At operation  204 , the in-line analyzer  142  measures a LPC value and an abrasive concentration value of the sampled slurry. 
     At operation  206 , the in-line analyzer  142  compares the LPC value of the sampled slurry with a first predetermined threshold. If the comparing result indicates that the LPC value of the sampled slurry is lower than or equal to the first predetermined threshold, operation  208  is then performed, where the in-line analyzer  142  generates an indication signal indicating that a LPC value of the slurry reaches a LPC target, and the controller  143  generates a control signal for controlling the filter  114  to stop filtering on the slurry in response to the indication signal. On the contrary, if the comparing result indicates that the LPC value of the sampled slurry is higher than the first predetermined threshold, operation  210  is then performed, where the in-line analyzer  142  determines whether the abrasive concentration value of the sampled slurry is in a predetermined specification range. 
     At operation  210 , if the determination result indicates that the abrasive concentration value of the sampled slurry is in the predetermined specification range, operation  212  is then performed, where the in-line analyzer  142  generates an indication signal indicating that an abrasive concentration value of the slurry meets a predetermined specification range, and the controller  143  generates a control signal for controlling the filter  114  to perform filtering on the slurry in response to the indication signal. In some embodiments, the control signal adjusts a filtering rate of the filter  114  based on a difference between the abrasive concentration value of the sampled slurry and the predetermined specification range. On the contrary, if the determination result indicates that the abrasive concentration value of the sampled slurry is out of the predetermined specification range, operation  214  is then performed, where the in-line analyzer  142  generates an indication signal indicating that the abrasive concentration value of the slurry does not meet the predetermined specification range, and the controller  143  generates a control signal for controlling the filter  114  to stop filtering on the slurry and switching the slurry source system  110  to a circulation mode to avoid over-filtration in response to the indication signal. 
     At operation  216 , the in-line analyzer  142  compares the LPC value of the sampled slurry with the first predetermined threshold. If the comparing result indicates that the LPC value of the sampled slurry is lower than or equal to the first predetermined threshold, operation  214  is then performed, where the in-line analyzer  142  generates an indication signal indicating that the LPC value reaches a LPC target, and the controller  143  generates a control signal for controlling the filter  114  to stop filtering on the slurry and switching the slurry source system  110  to a circulation mode to avoid over-filtration in response to the indication signal. On the contrary, if the comparing result indicates that the LPC value of the sampled slurry is higher than the first predetermined threshold, operation  218  is then performed, where the in-line analyzer  142  determines whether a lifetime of the filter  114  expires. 
     At operation  218 , if the determination result indicates that the lifetime of the filter  114  expires, operation  220  is then performed, where the in-line analyzer  142  generates an indication signal indicating the expiration of the filter  114 , and the controller  143  issues a notification accordingly, so as to inform that the filter  114  to be substituted with a new filter. After the operation  220 , operation  210  is then performed. On the contrary, if the determination result indicates that the lifetime of the filter  114  does not expire, operation  210  is then performed. 
     In some embodiments, analysis and determination of the abrasive concentration value of the sampled slurry, as illustrated in operations  204  and  210 , may be alternatively substituted by analyzing a zeta potential value of the sampled slurry and comparing the zeta potential of the sampled slurry with a second predetermined threshold, since the relationship between the abrasive concentration value and the zeta potential value is substantially linear. 
     By performing the method  200 , the operation of the circulation loop of the slurry source system  110  is controlled, and the filtering rate of the filter  114  is dynamically adjusted, such that the quantity of large particles in the slurry is automatically controlled. Therefore, automatic and dynamic control of the slurry dispersion system  100  is realized. 
       FIG. 3  is schematic diagram of a slurry dispersion system  300  in accordance with some embodiments. The slurry dispersion system  300  is utilized for providing a slurry to a polishing process such as CMP process or the like. In the present disclosure, the slurry dispersion system  300  is applied to a CMP tool which performs a CMP process, in which the slurry includes abrasive particles for abrasively removing a portion of a workpiece surface (such as a wafer surface). The slurry dispersion system  300  includes a slurry source system  310 , a reactor  320 , a slurry supply system  330  and a control system  340 . The slurry source system  310  includes a slurry drum  311 , a slurry pump  312 , a source tank  313 , a filter  314  and a three-way valve  315 . The slurry supply system  330  includes a supply tank  331  and a filter  332 . The supply tank  331  collects a mixed slurry from the reactor  320 , the filter  332  and the CMP process, and transports the mixed slurry to the filter  332  via a pump  331 A. The supply tank  331  also includes a pump  331 B for transporting the mixed slurry to the CMP process. Since the slurry source system  310 , the reactor  320  and the slurry supply system  330  are essentially the same as the slurry source system  110 , the reactor  120  and the slurry supply system  130  respectively, the details thereof are not described again herein. 
     The control system  340  includes a sampling valve  341 , an in-line analyzer  342  and a controller  343 . The sampling valve  341  samples the mixed slurry outputted from the supply tank  331  to obtain a sampled slurry. The in-line analyzer  342  measures at least one parameter of the sampled slurry. The parameter may include a LPC value, which is a value relative to the number of large particles of the mixed slurry, or include a zeta potential value, which is a value relative to the average electrical potential at a hydrodynamic slipping plane adjacent to a solid surface of each large particle exposed to a dispersing medium of the mixed slurry. In some embodiments, the parameter may further include a hydrogen ion concentration (pH) value, a specific gravity value and/or a chemical concentration value (e.g. hydrogen peroxide concentration value), but is not limited thereto. The in-line analyzer  342  generates an indication signal based on the parameter, in which the indication signal indicates at lease one characteristic of the mixed slurry. The controller  343  receives the indication signal, and generates a control signal based on the indication signal to perform a real time feedback control on the slurry dispersion system  300 . 
       FIG. 4  is flowchart diagram of a method  400  for controlling slurry quality of a slurry dispersion system in accordance with various embodiments. The method  400  may be operated in the slurry dispersion system  300  or other systems similar to the slurry dispersion system  300 . The following describes the method  400  operated in the control system  340  of the of the slurry dispersion system  300  for illustration. The method  400  begins at operation  402 , where the sampling valve  341  samples the mixed slurry outputted from the supply tank  331 , and allows the sampled slurry to be forwarded to the in-line analyzer  342 . At operation  404 , the in-line analyzer  342  measures a LPC value and a zeta potential value of the sampled slurry. 
     At operation  406 , the in-line analyzer  342  compares the LPC value of the sampled slurry and the zeta potential value with a first predetermined threshold and a second predetermined threshold respectively. If the comparing result indicates that the LPC value of the sampled slurry is higher than the first predetermined threshold, operation  408  is then performed, where the in-line analyzer  342  generates an indication signal indicating that a LPC value of the mixed slurry is higher than a LPC target, and the controller  343  generates a control signal for controlling the filter  332  to perform filtering on the mixed slurry. In some embodiments, the control signal adjusts a filtering rate of the filter  332  based on a difference between an abrasive concentration value of the sampled slurry and a predetermined specification range. In some embodiments, the in-line analyzer  342  further determines whether a lifetime of the filter  332  expires. If the determination result indicates that the lifetime of the filter  332  expires, the in-line analyzer  342  generates an indication signal indicating the expiration of the filter  332 , and the controller  343  issues a notification accordingly, so as to inform that the filter  332  to be substituted with a new filter. After operation  408 , operation  404  is then performed. 
     At operation  406 , if the comparing result indicates that the zeta potential value of the sampled slurry is higher than the second predetermined threshold, operation  410  is then performed, where the in-line analyzer  342  generates an indication signal indicating that a zeta potential value of the mixed slurry is higher than a zeta potential target, and the controller  343  generates a control signal for controlling the reactor  320  and the supply tank  331  to perform renewal of the mixed slurry stored in the supply tank  331 . In detail, for the renewal of the mixed slurry, the control signal directs the supply tank  331  to dump a quantity of the mixed slurry and directs the reactor  320  to provide the mixed tank slurry for the supply tank  331  with the same quantity. In some embodiments, the quantity of the mixed slurry to be removed from the supply tank  331  is (z−y)×V total /(x−y), where x is an initial zeta potential value of the mixed slurry outputted from the reactor  320 , y is the zeta potential value of the sampled slurry sampled from an output of the supply tank  331 , z is a target zeta potential value, V total  is the volume of the mixed slurry stored in the supply tank  331 , and z is higher than x. In some embodiments, the quantity of the mixed slurry to be removed from the supply tank  331  is (z′−y′)×V′ total /(x′−y′), where x′ is a source LPC value of the slurry from the source tank  313 , y′ is the LPC value of the sampled slurry sampled from an output of the supply tank  331 , z′ is a target LPC value, V′ total  is the volume of the mixed slurry stored in the supply tank  331 , and z′ is higher than x′. After operation  410 , operation  404  is then performed. 
     Otherwise, if the comparing result indicates that the LPC value of the sampled slurry is lower than or equal to the first predetermined threshold, and the zeta potential value of the sampled slurry is lower than or equal to the second predetermined threshold, the operation  412  is then performed, where the in-line analyzer  342  generates an indication signal indicating that the LPC value of the mixed slurry reaches the LPC target and that the zeta potential value of the mixed slurry reaches the zeta potential target, and the controller  343  generates control signals for controlling the filter  332  to stop filtering on the slurry and controlling the reactor  320  to stop transporting the mixed slurry to the supply tank  331  in response to the indication signal. 
     By performing the method  400 , the operation of the circulation loop of the slurry supply system  330  is controlled, and the filtering rate of the filter  332  is dynamically adjusted, such that the quantity of large particles in the slurry is automatically controlled. Also, instant renewal of the mixed slurry is performed to compensate for the quality of the mixed slurry that may be deteriorated due to aging effect. Therefore, automatic and dynamic control of the slurry dispersion system  300  is realized. 
       FIG. 5  is schematic diagram of a slurry dispersion system  500  in accordance with some embodiments. The slurry dispersion system  500  is utilized for providing a slurry to a polishing process such as CMP process or the like. In the present disclosure, the slurry dispersion system  500  is used for a CMP tool which performs a CMP process for illustration. As shown in  FIG. 5 , the slurry dispersion system  500  includes a slurry source system  510 , a reactor  520 , a slurry supply system  530  and a control system  540 . The slurry source system  510  includes a slurry drum  511 , a slurry pump  512 , a source tank  513 , a filter  514  and a three-way valve  515 . The slurry supply system  530  includes a supply tank  531  and a filter  532 . The supply tank  531  collects a mixed slurry from the reactor  520 , the filter  532  and the CMP process, and transports the mixed slurry to the filter  532  via a pump  531 A. The supply tank  531  also includes a pump  531 B for transporting the mixed slurry to the CMP process. Since the slurry source system  510 , the reactor  520  and the slurry supply system  530  are essentially the same as the slurry source system  110 , the reactor  120  and the slurry supply system  130  respectively, the details thereof are not described again herein. 
     The control system  540  includes sampling valves  541 A,  541 B and  541 C, an in-line analyzer  542  and a controller  543 . The sampling valve  541 A samples the slurry outputted from the source tank  513  to obtain a first sampled slurry. The sampling valve  541 B samples the mixed slurry outputted from the reactor  520  to obtain a second sampled slurry. The sampling valve  541 C samples the mixed slurry outputted from the supply tank  531  to obtain a third sampled slurry. The in-line analyzer  542  measures at least one parameter of the first, second and third sampled slurry. The parameter may include a LPC value, which is relative to the number of large particles of the slurry, and/or include a zeta potential value, which is relative to the average electrical potential at a hydrodynamic slipping plane adjacent to a solid surface of each large particle exposed to a dispersing medium of the slurry. The in-line analyzer  542  generates an indication signal based on the parameter, in which the indication signal indicates at lease one characteristic of the slurry and/or the mixed slurry. In some embodiments, the parameter may further include a pH value, a specific gravity value and/or a chemical concentration value (e.g. hydrogen peroxide concentration value), but is not limited thereto. The controller  543  receives the indication signal, and generates a control signal based on the indication signal to perform a real time feedback control on the slurry dispersion system  500 . In some embodiments, the controller  543  is a programmable logic controller (PLC) for real time feedback control on the slurry dispersion system  500  over one or more conditions corresponding to the indication signal. 
     In the slurry dispersion system  500 , the sampling valves  541 A,  541 B and  541 C are configured to sample the slurry outputted from the source tank  513  and the mixed slurry outputted from the reactor  520  and the supply tank  531 , so as to obtain the first sampled slurry, the second sampled slurry and the third sampled slurry separately. The indication signal may be generated in relation to the first sampled slurry, the second sampled slurry, the three sampled slurry and/or combinations thereof. In addition, the controller  543  may further adjust, for example, a flow rate of the slurry flowing into the reactor  520 , titration of the chemical titrated into the reactor  520 , and/or other adjustable factors in the slurry dispersion system  500 . 
       FIG. 6  is a flowchart diagram of a method  600  for real time feed-back controlling a slurry dispersion system in accordance with various embodiments. The method  600  is operated in a slurry dispersion system such as that shown in  FIG. 1 ,  FIG. 3  or  FIG. 5 , and/or other suitable slurry dispersion systems. 
     The method  600  begins at operation  602 , where a slurry is sampled from the slurry dispersion system to obtain a sampled slurry. The sampled slurry may be undiluted or be mixed with at least one chemical. The chemical may include, but is not limited to, hydrogen peroxide, potassium and/or ammonium hydroxide. 
     At operation  604 , at least one parameter of the sampled slurry is measured. The parameter may include a LPC value, which is relative to the number of large particles of the slurry, and/or include a zeta potential value, which is relative to the average electrical potential at a hydrodynamic slipping plane adjacent to a solid surface of each large particle exposed to a dispersing medium of the slurry. In some embodiments, the parameter may further include a pH value, a specific gravity value and/or a chemical concentration value (e.g. hydrogen peroxide concentration value), but is not limited thereto. 
     At operation  606 , an indication signal is generated based on the parameter. The indication signal indicates at lease one characteristic of the slurry, such as a LPC value and/or a zeta potential value of the slurry. The indication signal is generated by comparing the LPC value with a first predetermined threshold, or by comparing the zeta potential value with a second predetermined threshold. In some embodiments, the characteristic may further include a pH value, a specific gravity value and/or a chemical concentration value (e.g. hydrogen peroxide concentration value) of the slurry, but is not limited thereto. 
     At operation  608 , a control signal is generated based on the indication signal. The control signal is used to perform a real time feedback control on the slurry dispersion system for controlling quality of the slurry in the slurry dispersion system. In some embodiments, the control signal instructs a supply tank of the slurry dispersion system to dump a quantity of the mixed slurry and directs a reactor of the slurry dispersion system to provide the mixed slurry for the supply tank with the same quantity. In some embodiments, the quantity of the mixed slurry to be removed from the supply tank is (z−y)×V total /(x−y), where x is an initial zeta potential value of the mixed slurry outputted from the reactor, y is the zeta potential value of the sampled slurry sampled from an output of the supply tank, z is a target zeta potential value, V total  is the volume of the mixed slurry stored in the supply tank, and z is higher than x. In alternative embodiments, the quantity of the mixed slurry to be removed from the supply tank is (z′−y′)×V′ total /(x′−y′), where x′ is a source LPC value of the slurry of a slurry source system of the slurry dispersion system, y′ is the LPC value of the sampled slurry sampled from an output of the supply tank, z′ is a target LPC value, V′ total  is the volume of the mixed slurry stored in the supply tank, and z′ is higher than x′. 
     In accordance with some embodiments, the present disclosure discloses a slurry dispersion system comprising a slurry source system, a reactor, a slurry supply system, an in-line analyzer and a controller. The slurry source system is configured to provide an undiluted slurry. The reactor is connected to the slurry source system, wherein the reactor is configured to mix the undiluted slurry with at least one chemical to obtain and transport a mixed slurry. The slurry supply system is connected to the reactor, wherein the slurry supply system is configured to store the mixed slurry transported from the reactor and to output the mixed slurry to a chemical mechanical polishing (CMP) tool. The in-line analyzer is connected to the slurry supply system. The in-line analyzer is configured to measure parameters that include a large particle count (LPC) value of a sampled slurry sampled from the slurry supply system, and generate a first indication signal in response to the LPC value being greater than a first predetermined threshold. The controller is electrically connected to the in-line analyzer and a filter of the slurry supply system. The controller is configured to turn on the filter to start filtering the mixed slurry in response to the first indication signal. 
     In accordance with some embodiments, the present disclosure discloses a slurry dispersion system comprising a slurry source system, a reactor, a slurry supply system, an in-line analyzer and a controller. The slurry source system is configured to provide an undiluted slurry. The reactor is connected to the slurry source system, wherein the reactor is configured to mix the undiluted slurry with at least one chemical to obtain and transport a mixed slurry. The slurry supply system is connected to the reactor, wherein the slurry supply system is configured to store the mixed slurry transported from the reactor and to output the mixed slurry to a chemical mechanical polishing (CMP) tool. The in-line analyzer is connected to the slurry supply system. The in-line analyzer is configured to: measure parameters that include a large particle count (LPC) value and a zeta potential value of a sampled slurry sampled from the slurry supply system, and generate a first indication signal in response to the LPC value being smaller than a first predetermined threshold and the zeta potential value being smaller than a second predetermined threshold. The controller is electrically connected to the in-line analyzer and a filter of the slurry supply system. The controller is configured to turn off the filter to stop filtering the mixed slurry in response to the first indication signal. 
     In accordance with some embodiments, the present disclosure discloses a method for feed-back control of a slurry dispersion system. The method includes sampling the mixed slurry to obtain a sampled slurry, determining whether a zeta potential value of the sampled slurry is greater than a first predetermined threshold, and performing a renewal of the mixed slurry in response to determining that the zeta potential value is greater than the first predetermined threshold. 
     The foregoing 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 should 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 should 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.