Patent Publication Number: US-8992287-B2

Title: Slurry supply system for CMP process

Description:
BACKGROUND 
     Integrated chips are constructed using complex fabrication processes that form a plurality of different layers on top of one another. Many of the layers are patterned using photolithography, in which a light sensitive photoresist material is selectively exposed to light. For example, photolithography is used to define back end metallization layers that are formed on top of one another. To ensure that the metallization layers are formed with a good structural definition, the patterned light must be properly focused. To properly focus the pattered light, a workpiece must be substantially planar to avoid depth of focus problems. 
     Chemical mechanical polishing (CMP) is a widely used process by which both chemical and physical forces are used to globally planarize a semiconductor workpiece. The planarization prepares the workpiece for the formation of a subsequent layer. A typically CMP system comprises a rotating platen covered by a polishing pad. A slurry distribution system is configured to provide a polishing mixture, having abrasive components, to the polishing pad. A workpiece is then brought into contact with the pad, causing the rotating platen to planarize the workpiece. 
     SUMMARY 
     The following presents a simplified summary in order to provide a basic understanding of one or more aspects of the disclosure. This summary is not an extensive overview of the disclosure, and is neither intended to identify key or critical elements of the disclosure, nor to delineate the scope thereof. Rather, the primary purpose of the summary is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description that is presented later. 
     In some embodiments, the present disclosure relates to a slurry distribution system for a chemical mechanical polishing tool. The slurry distribution system comprises a mixing tank configured to generate a polishing mixture comprising a diluted slurry mixture having abrasive particles that enable mechanical polishing of a workpiece. A transport piping is configured to transport the polishing mixture between the mixing tank and a chemical mechanical polishing (CMP) tool. An energy source is in direct communication with the transport piping. The energy source is configured to transfer energy to the abrasive particles within the transport piping, thereby preventing accumulation of the abrasive particles within the transport piping. 
     In another embodiment, the present disclosure relates to a slurry distribution system for a chemical mechanical polishing tool. The slurry distribution system comprises a mixing tank configured to generate a polishing mixture comprising a diluted slurry mixture having abrasive particles that enable mechanical polishing of a workpiece. A double tube is connected between the mixing tank and a chemical mechanical polishing (CMP) tool. The double tube comprises a first tube configured to transport the polishing mixture between the mixing tank and the CMP tool and a second tube configured to transport a stimulating liquid. An energy source is configured to transfer energy to the stimulating liquid, which subsequently transfers the energy to the abrasive particles within the first tube, thereby preventing accumulation of the abrasive particles within the first tube. 
     In another embodiment, the present disclosure relates to a method for distributing slurry for a chemical mechanical polishing tool. The method comprises transporting a polishing mixture comprising a diluted slurry mixture having abrasive particles between a mixing tank and a chemical mechanical polishing tool by way of a first tube. Energy is provided to a stimulating element in contact with the first tube over a majority of a length of the first tube, wherein the stimulating element is configured to transfer energy to the abrasive particles within the first tube, thereby preventing accumulation of the abrasive particles within the first tube. 
     The following description and annexed drawings set forth in detail certain illustrative aspects and implementations of the disclosure. These are indicative of but a few of the various ways in which the principles of the disclosure may be employed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  illustrates block diagram of a typical slurry distribution system. 
         FIGS. 1   b - 1   c  illustrate cross sectional view of a transport piping connecting a mixing tank and a chemical mechanical polishing tool within the slurry distribution system of  FIG. 1   a.    
         FIG. 2  illustrates a block diagram of some embodiments of a slurry distribution system as provided herein. 
         FIG. 3  illustrates a cross sectional view of some embodiments of a transport piping comprising a double tube. 
         FIG. 4  illustrates a cross sectional view of an embodiments of a transport piping comprising a double tube. 
         FIG. 5  illustrates a three-dimensional view of an embodiment of a double tube. 
         FIG. 6  illustrates a block diagram of some alternative embodiments of a slurry distribution system as provided herein. 
         FIG. 7   a  illustrates a cross sectional view of an embodiment of a transport piping comprising two polishing mixture transport pipes. 
         FIG. 7   b  illustrates a cross sectional view of an alternative embodiment of a transport piping comprising two polishing mixture transport pipes. 
         FIG. 8  illustrates some embodiments of a slurry distribution system, wherein a stimulating liquid is provided to a cleaning element configured to enable cleaning of one or more parts of a CMP tool. 
         FIG. 9  illustrates a block diagram of an alternative embodiments of a slurry distribution system as provided herein. 
         FIG. 10  is a flow diagram of some embodiments of a method for distributing a slurry based polishing mixture to a chemical mechanical polishing tool. 
     
    
    
     DETAILED DESCRIPTION 
     The description herein is made with reference to the drawings, wherein like reference numerals are generally utilized to refer to like elements throughout, and wherein the various structures are not necessarily drawn to scale. In the following description, for purposes of explanation, numerous specific details are set forth in order to facilitate understanding. It may be evident, however, to one of ordinary skill in the art, that one or more aspects described herein may be practiced with a lesser degree of these specific details. In other instances, known structures and devices are shown in block diagram form to facilitate understanding. 
       FIG. 1   a  illustrates a block diagram of a slurry distribution system  100 . The slurry distribution system  100  comprises a mixing tank  102  configured to mix a concentrated slurry with de-ionized water to form a polishing mixture. The polishing mixture is transported from the mixing tank  102  to one or more chemical mechanical polishing (CMP) tools  104  by way of a transport piping  106 . 
       FIG. 1   b  illustrates a cross sectional view  108  of a transport piping  106  in slurry distribution system  100 . During transport of the polishing mixture, abrasive particles  110  within the polishing mixture precipitate from the polishing mixture and condense on sidewalls of the transport piping  106 . Over time, the condensation of abrasive particles  110  within the polishing mixture builds up on the sidewalls of the transport piping  106 , resulting in relatively large accumulations  112  of abrasive particles. 
     The inventors have appreciated large chunks of the accumulations  112  can break loose from the sidewall of the transport piping  106 . As shown in the cross sectional view  114  of  FIG. 1   c , the chunks of accumulation  116  can travel through the transport piping  106  to the one or more CMP tools  104  (e.g., shown in  FIG. 1   a ). When the large chunks of accumulation  116  are provided to the one or more CMP tools  104 , they are brought into contact with a workpiece during the polishing process. In contrast to the relatively small abrasive particles  110 , which aid in the CMP polishing process, the large chunks of accumulation  116  result in micro-scratches and other defects within the surface of the workpiece. 
     Accordingly, some aspects of the present disclosure provide for a slurry distribution system for a chemical mechanical polishing (CMP) tool that prevents the accumulation of abrasive particles within the distribution system. In some embodiments, the slurry distribution system comprises a mixing tank, which is configured to generate a polishing mixture comprising a diluted slurry having abrasive particles that enable mechanical polishing of a workpiece. The polishing mixture is transported between the mixing tank and a CMP tool by way of a transport piping. An energy source is configured to transfer energy to a stimulating element that is in communication with the transport piping along a majority of its length. The stimulating element further transfers the energy to abrasive particles within the polishing mixture, thereby preventing accumulation of the abrasive particles within the transport piping. 
       FIG. 2  illustrates a block diagram of some embodiments of a slurry distribution system  200  as provided herein. The slurry distribution system  200  comprises a mixing tank  102  connected to one or more CMP tools  104  by way of a transport piping  202 . 
     The mixing tank  102  is configured to mix a concentrated slurry solution with a diluting agent, such as de-ionized water, to form a polishing mixture. The polishing mixture content may vary depending upon a material that is to be polished by the CMP tool  104 . In general, the polishing mixture comprises a dilute slurry having abrasive particles that are used in mechanical polishing of a workpiece and one or more chemicals (e.g., H 2 O 2 , NH 4 OH, etc.) that are used in chemical polishing of the workpiece. 
     The transport piping  202  is configured to transfer the polishing mixture between the mixing tank  102  and the one or more CMP tools  104 . An energy source  204  is configured to provide electrical energy to a stimulating element  206  in communication with the transport piping  202 . The stimulating element  206  is configured to convert the electrical energy to another form of energy, which is transferred to the abrasive particles within the polishing mixture. In some embodiments, the energy source  204  and stimulating element  206  comprise an atomizer configured to transfer energy through momentum and/or heat transfer. In other embodiments, the energy source  204  and stimulating element  206  may utilize alternative energy transport methodology. The transferred mechanical energy prevents the abrasive particles from condensing/accumulating on the sidewall of the transport piping  202 . By preventing accumulation of abrasive particles, the formation of large chunks of accumulation within the transport piping  202  is avoided and wafer defects resulting from the large chunks of accumulation are prevented. 
     In some embodiments, the stimulating element  206  is comprised within the transport piping  202 . In other embodiments, the stimulating element  206  is located external to the transport piping  202 . In some embodiments, the stimulating element  206  runs along a length of the transport piping  202 . In one such embodiment, the stimulating element  206  is configured to transfer energy to abrasive particles that are located in close proximity to the stimulating element  206 , rather than to abrasive particles throughout the entire length of the transport piping  202 . For example, in an embodiment, the stimulating element  206  may transfer energy in a substantially radial direction to abrasive particles within the transport piping  202 . 
     In some embodiments, the transport piping  202  and stimulating element  206  comprise a double tube comprising one tube that is configured to transport polishing mixture and another tube that is operated as a stimulating element.  FIG. 3  illustrates a cross sectional view of some embodiments of a transport piping comprising a double tube  300 . Although,  FIG. 3  illustrates the first tube  302  and the second tube  304  as coaxial tubes, such that the first tube  302  is concentric with the second tube  304 , it will be appreciated that this is a non-limiting embodiment. In other embodiments, the first tube  302  and the second tube  304  are not concentric with each other. Furthermore, it will be appreciated that the term “double tube” as provided herein is not limited to structural configurations comprising two tubes, but may include structural configurations having one or more tubes comprised within another tube. 
     Double tube  300  comprises a first tube  302  and a second tube  304 , wherein the second tube  304  is comprised within the first tube  302 . In some embodiments, the second tube  304  is comprised within the first tube  302  along the entire length of the first tube  302 . This causes the liquid within the first tube  302  to be in contact with the second tube  304  along the entire length of the second tube  304 . 
     One of the first tube  302  or the second tube  304  is configured to transport a polishing mixture, while the other of the first tube  302  or second tube  304  is configured to comprise a stimulating liquid that operates as a stimulating element (e.g., corresponding to stimulating element  206  in  FIG. 2 ). An energy source  204  is connected to the tube comprising a stimulating liquid and is configured to provide energy to the stimulating liquid therein. The energy is subsequently transferred from the stimulating liquid to abrasive particles within the polishing mixture. Therefore, the structure of the double tube  300  allows for the energy to be easily transferred from the energy source  204  to the abrasive particles along a length of the double tube  300 . 
     In some embodiment, shown in the cross sectional view  400  of  FIG. 4 , the outer, first tube  302  is configured to transport a stimulating liquid, while the inner, second tube  304  is configured to transport a polishing mixture comprising abrasive particles. In such embodiments, the energy source  204  is connected to the first tube  302 , which operates as a stimulating element. The energy source  204  is configured to provide electrical energy to the stimulating liquid within the first tube  302 . The stimulating liquid converts the energy to another form and then transfers the converted energy to abrasive particles within the second tube  304 . 
     It will be appreciated that a stimulating element (e.g., corresponding to element  206  in  FIG. 2 ) may extend along the entire length of the transport piping (e.g., element  202 ) or along some subset of the entire length.  FIG. 5  illustrates a three dimensional view of a double tube  500 , wherein the stimulating element extends along a subset of the entire length the transport piping. As shown in  FIG. 5 , a first tube  302  comprises a stimulating liquid and a second tube  304  comprises a polishing mixture. The first tube  302  of the double tube extends along a first length L 1  and the second tube  304  of the double tube extends along a second length L 2 , wherein L 2  is larger than L 1 . 
     In some embodiments, the disclosed slurry distribution system may comprise a plurality of stimulating elements, respectively having a length less than that of the transport piping comprising the polishing mixture. The plurality of stimulating elements are configured to extend along a portion of the transportation piping comprising the polishing mixture. For example, in an exemplary embodiment, the transport piping may comprise a plurality of stimulating elements that extend discontinuously along the transportation piping comprising the polishing mixture. In such an embodiment, each of the stimulating elements is configured to transport energy to the polishing mixture. 
     In some embodiments, the energy source is configured to generate energy within the stimulating liquid using an ultrasonic energy source. In one such embodiment, the energy source comprises one or more ultrasonic transducers  502  configured to provide energy to the stimulating liquid at a frequency of about 0-500 kHz, for example. 
     The one or more ultrasonic transducers  502  are configured to convert electrical energy to high frequency mechanical energy. The high frequency mechanical energy produces pressure waves  504  within the stimulating liquid. The pressure waves  504  travel through the stimulating liquid along the length of the double tube. The pressure waves  504  alternate between high pressure waves and low pressure waves, such that the stimulating liquid is compressed by the high pressure waves and decompressed by the low pressure waves. As the low pressure waves decompress the stimulating liquid, cavities form within the stimulating liquid. The high pressure waves then compresses the cavities, causing the cavities to implode and release energy. The energy is transferred to abrasive particles within the second tube  304  as mechanical energy. The mechanical energy prevents the accumulation of abrasive material on the walls of the second tube  304 . 
       FIG. 6  illustrates a block diagram of additional embodiments of a slurry distribution system  600  as provided herein. The slurry distribution system  600  comprises a mixing tank  102  connected to a transport piping comprising a first polishing mixture supply line  602   a  and a second polishing mixture supply line  602   b . The mixing tank  102  is configured to receive an undiluted concentrated slurry, de-ionized water, and chemicals, and to mix together the undiluted slurry with the de-ionized water and chemicals to form a polishing mixture. The polishing mixture is provided to one or more valve manifold boxes  604 , by way of the first and second polishing mixture supply lines,  602   a  and  602   b . A valve manifold boxes  604  selectively provides the polishing mixture from the first or second polishing mixture supply lines,  602   a  and  602   b , to a CMP tool  104  when the CMP tool  104  is operated to perform a chemical mechanical polishing. 
     In some embodiments, the first and second polishing mixture supply lines,  602   a  and  602   b , comprise a distribution piping and a re-circulation piping. The distribution piping is configured to provide a polishing mixture from the mixing tank  102  to the one or more valve manifold boxes  604 . The re-circulation piping is configured to return polishing mixture that has not been provided to the CMP tool  104  from the one or more valve manifold boxes  604  to the mixing tank  102 , where the polishing mixture is further mixed to prevent precipitation of abrasive particles within the polishing mixture. 
     The energy source  204  is configured to provide energy to abrasive particles within both the first and second polishing mixture supply lines,  602   a  and  602   b , by way of one or more stimulating elements. In some embodiments, the energy source  204  is coupled to a single stimulating element  206  that is configured to transfer energy along a length of the first and second polishing mixture supply lines  602   a  and  602   b . In some other embodiments, the energy source is coupled to a first stimulating element  206   a  in contact with transport piping upstream of the one or more valve manifold boxes  604  and a second stimulating element  206   b  in contact with transport piping downstream of the one or more valve manifold boxes  604 . 
       FIG. 7   a  illustrates an embodiment of a double tube  700  comprising first and second polishing mixture supply lines,  602   a  and  602   b . The double tube comprises a first stimulating tube  702   a  and a second stimulating tube  702   b  operating as a stimulating element. The first stimulating tube  702   a  comprises the first polishing mixture supply line  602   a  and the second stimulating tube  702   b  comprises the second polishing mixture supply line  602   b . A stimulating liquid is comprised within the first and second stimulating tubes,  702   a  and  702   b . An energy source  204  is configured to transfer energy to the stimulating liquid within the first and second stimulating tubes,  702   a  and  702   b . The stimulating liquid operate as stimulating elements that respectively provide energy to abrasive particles within the first and second polishing mixture supply lines,  602   a  and  602   b.    
       FIG. 7   b  illustrates an alternative embodiment of a double tube transport piping  704  comprising first and second polishing mixture supply lines,  602   a  and  602   b . The double tube comprises a single stimulating tube  702  operating as a stimulating element. The single stimulating tube  702  comprises both the first and second polishing mixture supply lines,  602   a  and  602   b . A stimulating liquid is comprised within the single stimulating tube  702 . An energy source  204  is configured to transfer energy to the stimulating liquid. The stimulating liquid operates as a stimulating element that provides energy to the first and second polishing mixture supply lines,  602   a  and  602   b.    
     In some embodiments, the slurry distribution system is configured to provide the stimulating liquid to a CMP tool for processes related to the CMP tool operation.  FIG. 8  illustrates some embodiments of a slurry distribution system  800 , wherein a stimulating liquid is provided to a cleaning element  802  configured to enable cleaning of one or more parts of a CMP tool  104 . By cleaning the CMP tool  104 , polishing efficiency of the CMP tool  104  is improved. 
     In some embodiments, the stimulating liquid is provided to a cleaning element  802  configured to clean a CMP polishing pad of the CMP tool  104  after polishing of a workpiece is performed. For example, one of ordinary skill in the art will appreciate that slurry accumulation on a CMP polishing pad causes a roughening of the polishing pad surface. Therefore, the stimulating liquid can be provided from the stimulating element  206  to a polishing pad of the CMP tool  104  to remove slurry accumulation from the polishing pad surface. 
     In some embodiments, the stimulating liquid may be provided from the stimulating element  206  to a cleaning element  802  comprising a high pressure micro jet system configured to condition the CMP polishing pad. In such an embodiment, the stimulating liquid may comprise de-ionized water. The high pressure micro jet system is configured to highly pressurize (e.g., 10-30 MPa) the de-ionized water, before it is sprayed as small droplets onto the CMP polishing pad with a high speed. The water droplets condition the polishing pad, for example, by removing debris and slurry residue. 
       FIG. 9  illustrates a block diagram of another embodiment of a slurry distribution system  900 , wherein the stimulating liquid is provided from a stimulating liquid source to at least one stimulating tube of a transport piping comprising a double tube. 
     As shown in  FIG. 9 , a transport piping comprises a first and second polishing mixture supply lines  602   a  and  602   b  and a stimulating tube  904  configured to comprise a stimulating liquid. The first and second polishing mixture supply lines  602   a  and  602   b , are configured to transport polishing mixture between the mixing tank  102  and one or more valve manifold boxes  604 . The stimulating tube  904  is configured to circulate the stimulating liquid along the length of the first and second polishing mixture supply lines  602   a  and  602   b , so as to keep the stimulating liquid in contact with the first and second polishing mixture supply lines,  602   a  and  602   b.    
     The stimulating tube  904  is connected to a stimulating liquid source  902  by way of a first conduit  906 . The stimulating liquid source  902  is configured to provide stimulating liquid to the stimulating tube  904 . In some embodiments, the stimulating tube comprise a plurality of stimulating tubes, operated separately. For example, a first value is operable to provide liquid from the stimulating liquid source  902  to a first stimulating tube, while a second value is operable to provide stimulating liquid from the stimulating liquid source  902  to a second stimulating tube. 
     In some embodiments, the stimulating liquid source  902  comprises a tank containing a stimulating liquid. In one such embodiment, the stimulating liquid source  902  provides de-ionized water to the stimulating tube  904  by way of the first conduit  906 , while a second conduit  908  may be configured to provide the stimulating liquid back to the stimulating liquid source  902 . In another embodiment, the stimulating liquid source  902  comprises a de-ionized water tap. In one such embodiment, the stimulating liquid source  902  provides de-ionized water to the stimulating tube  904  by way of the first conduit  906 , while the de-ionized water is removed from the stimulating tube  904 , by way of a third conduit  910  connected to an open drain  912 . 
     In some embodiments, the stimulating tube  904  operate as a closed system. For example, the stimulating liquid source  902  and the stimulating tube  904  comprise a fluid system that is closed (i.e., that is self contained). The closed system can be easily added to the structure of existing CMP slurry distribution systems. 
       FIG. 10  illustrates a flow diagram of some embodiments of a method  1000  for distributing a slurry based polishing mixture to a chemical mechanical polishing tool. While the method  1000  provided herein is illustrated and described below as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events are not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects or embodiments of the description herein. Further, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases. 
     At  1002  a polishing mixture is transported between a mixing tank and a chemical mechanical polishing tool by way of one tube of a double tubing. The polishing mixture comprises a diluted slurry having abrasive particles that enable the chemical mechanical polishing tool to mechanically polish a workpiece. 
     At  1004  energy is provided to a stimulating element in contact with the first tube over a majority of a length of the first tube. The stimulating element is configured to transfer energy to the abrasive particles within the first tube, thereby preventing accumulation of the abrasive particles within the first tube. In various embodiments the stimulating element may transfer the energy by way momentum, heat, or other forms of energy transfer. 
     In some embodiments, providing energy to a stimulating element comprises providing a simulating liquid is provided to a second tube of the double tubing at  1006 . In some embodiments, the second tube surrounds the first tube so as to keep the stimulating liquid in contact with the first tube containing the polishing mixture. In some embodiments, the stimulating liquid comprises de-ionized water. 
     At  1008  energy is provided to the stimulating liquid. In some embodiments, energy is provided to the stimulating liquid by converting electrical energy to a high frequency mechanical energy that produces ultrasonic pressure waves within the stimulating liquid. 
     Therefore, the method  1000  prevents the accumulation of abrasive particles within the double tubing, preventing the formation of large chunks of accumulation which damage a workpiece during chemical mechanical polishing. 
     It will be appreciated that equivalent alterations and/or modifications may occur to one of ordinary skill in the art based upon a reading and/or understanding of the specification and annexed drawings. The disclosure herein includes all such modifications and alterations and is generally not intended to be limited thereby. In addition, while a particular feature or aspect may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features and/or aspects of other implementations as may be desired. Furthermore, to the extent that the terms “includes”, “having”, “has”, “with”, and/or variants thereof are used herein, such terms are intended to be inclusive in meaning—like “comprising.” Also, “exemplary” is merely meant to mean an example, rather than the best. It is also to be appreciated that features, layers and/or elements depicted herein are illustrated with particular dimensions and/or orientations relative to one another for purposes of simplicity and ease of understanding, and that the actual dimensions and/or orientations may differ substantially from that illustrated herein.