Patent Publication Number: US-7223157-B2

Title: Chemical-mechanical polishing apparatus and method of conditioning polishing pad

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a chemical-mechanical polishing (CMP) apparatus. More particularly, the present invention relates to a chemical-mechanical polishing (CMP) apparatus and a method of conditioning a polishing pad capable of improving the polishing effect. 
     2. Description of the Related Art 
     With the trend of minimized device dimensions, the resolution of photo-exposure needs to be correspondingly increased. Furthermore, as the depth of a photolithography-exposure reduces, the tolerance for any undulation in the surface profile of the chip is lower. Chemical-mechanical polishing is currently one of the techniques capable of providing global planarization to an ultra-large scale integrated (ULSI) circuit. Aside from planarizing the surface profile of a chip, the anisotropic polishing characteristic of the chemical-mechanical polishing process is applied to fabricate vertical and horizontal metallic interconnects through metal polishing operations, to fabricate shallow trench isolation structures in an front stage manufacturing process or advanced device, to planarize micro-electromechanical system or to fabricate flat panel display. 
       FIG. 1  is a schematic drawing of a conventional chemical-mechanical polishing apparatus. As shown in  FIG. 1 , the conventional chemical-mechanical polishing apparatus  100  comprises at least a polishing platen  110 , a polishing pad  120 , a slurry supplying piping  130 , a polishing pad conditioner  150  and a chemical reagent supplying piping  160 . 
     In  FIG. 1 , the surface of the polishing platen  110  further comprises a plurality of slurry outlets  112 . The polishing pad  120  is disposed on the polishing platen  110 . The polishing platen  110  drives the polishing pad  120  to spin through a carrier platform (not shown). With the delivery of slurry, a chemical-mechanical polishing process is carried out to planarize a chip or any structure requiring global planarization in a semiconductor fabrication process. 
     The slurry supplying piping  130  is connected to the bottom of the polishing platen  110 . The slurry is delivered from a slurry supplying tank  140  through the slurry supplying piping  130  underneath the polishing platen  110  and the slurry outlet  112  to the surface of the polishing pad  120 . Because the polishing agent is slurry, the slurry outlet  112  may be blocked if the concentration of the slurry is too high or some dregs are clogged up in the slurry outlet  112 . As a result, a blocked slurry outlet  112  can not deliver slurry to the polishing pad  120  evenly. The non-uniform slurry distribution on the polishing pad may have some effects on the planarity in subsequent chemical-mechanical polishing process. In some cases, defects will be formed in the fabricated devices. 
     As shown in  FIG. 1 , the polishing pad conditioner  150  is disposed on the polishing pad  120 . The chemical reagent supplying piping  160  is connected between the polishing pad conditioner  150  and a chemical reagent supplying tank  170 . The chemical reagent in the chemical reagent supplying tank  170  is delivered to the polishing pad conditioner  150  through the chemical reagent supplying piping  160 . 
     At the end of a polishing operation, slurry dregs sometimes are attached to the surface of the polishing pad  120 . When this happens, the polishing pad conditioner  150  can adjust the condition on the polishing pad  120  by removing dregs from the surface of the polishing pad  120 . However, the delivering of chemical reagent to the polishing pad conditioner  150  only has a limited conditioning effect on the polishing pad  120 . 
     SUMMARY OF THE INVENTION 
     Accordingly, one objective of the present invention is to provide a chemical-mechanical polishing apparatus suitable for improving chemical-mechanical polishing operation as well as polishing pad conditioning operation. 
     Another objective of the present invention is to provide a method of conditioning a polishing pad such that the conditioned polishing pad can improve the polishing effect in a chemical-mechanical polishing operation. 
     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a chemical-mechanical polishing apparatus. The chemical-mechanical polishing apparatus comprises at least a polishing platen, a polishing pad, a slurry supplying piping, a polishing pad conditioner, a chemical reagent supplying piping and a splitting piping. The surface of the polishing platen comprises a plurality of slurry outlets. The polishing pad is disposed on the polishing platen. The slurry supplying piping is connected to the bottom of the polishing platen, suitable for delivering slurry from under the polishing platen to a polishing pad surface through the slurry outlets. The polishing pad conditioner is disposed over the polishing pad. The chemical reagent supplying piping is connected to the polishing pad conditioner for supplying chemical reagent to the polishing conditioner. The splitting piping is connected between the slurry supplying piping and the chemical reagent supplying piping and is suitable for delivering chemical reagent through the chemical reagent supplying piping, the slurry supplying piping and the slurry outlets to the polishing pad surface. 
     According to the aforementioned chemical-mechanical polishing apparatus of the present invention, the splitting piping further comprises a first control valve and the slurry supplying piping further comprises a second control valve. To supply slurry to the polishing pad, the first control valve is shut while the second control valve is opened. On the other hand, to supply chemical reagent to the polishing pad, the first control valve is opened while the second control valve is shut. 
     The present invention also provides a polishing pad conditioning method suitable for the aforementioned chemical-mechanical polishing apparatus. The polishing pad conditioning method comprises providing chemical reagent to a polishing pad conditioner through the chemical reagent supplying piping after polishing the to-be-polished layer on a wafer using the chemical-mechanical polishing apparatus. In the meantime, the chemical reagent is also delivered to the polishing pad through the splitting piping and the slurry supplying piping. The polishing pad conditioner is used to condition the surface of the polishing pad. 
     According to the aforementioned polishing pad conditioning method of the present invention, the to-be-polished layer on the wafer includes a metallic layer. 
     According to the aforementioned polishing pad conditioning method of the present invention, the metallic layer comprises copper and the slurry comprises an acid solution and the chemical reagent comprises an acid solution such as a folic acid containing solution. 
     According to the aforementioned polishing pad conditioning method of the present invention, the metallic layer comprises tungsten and the slurry comprises an acid solution and the chemical reagent comprises a deionized water. 
     According to the aforementioned polishing pad conditioning method of the present invention, the metallic layer comprises tantalum nitride and the slurry comprises an alkaline solution and the chemical reagent comprises a deionized water. 
     In the present invention, a chemical reagent supplying piping capable of delivering chemical reagent above and below the polishing pad is provided. Thus, chemical reagent can be delivered to the polishing pad via the bottom of the polishing platen to dissolve any slurry dregs blocking the slurry outlets. Hence, the slurry can be more uniformly distributed on the polishing pad surface in a subsequent polishing process to improve the polishing effect. In addition, the chemical reagent for conditioning the polishing pad is delivered to the polishing pad from above and below so that the chemical reagent can be uniformly distributed on the surface of the polishing pad, which can better condition the polishing pad and provide better polishing effect in a subsequent chemical-mechanical polishing process. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic drawing of a conventional chemical-mechanical polishing apparatus. 
         FIG. 2  is a schematic drawing of a chemical-mechanical polishing apparatus according to one embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
       FIG. 2  is a schematic drawing of a chemical-mechanical polishing apparatus according to one embodiment of the present invention. As shown in  FIG. 2 , the chemical-mechanical polishing apparatus  200  of the present embodiment comprises at least a polishing platen  210 , a polishing pad  220 , a slurry supplying piping  230 , a polishing pad conditioner  250 , a chemical reagent supplying piping  260  and a splitting piping  280 . 
     As shown in  FIG. 2 , the polishing platen  210  is disposed on a carrier platform (not shown). The polishing platen  210  is spun driven by the carrier platform. The polishing pad  220  is disposed on the polishing platen  210 , and spins with the polishing platen  210  to polish the to-be-polished layer. 
     As shown in  FIG. 2 , the surface of the polishing platen  210  comprises a plurality of slurry outlets  212 . The slurry supplying piping  230  is connected to the bottom of the polishing platen  210 , suitable for supplying slurry from under the polishing platen  210  to the surface of the polishing pad  220  via the slurry outlets  212 . The surface of the polishing pad  210  also comprises a plurality of tiny holes (not shown). The holes facilitate the transportation of slurry to the polishing surface of the polishing pad  210  such that the polishing pad  210  may perform the polishing operation on a to-be-polished layer. 
     As shown in  FIG. 2 , the polishing pad conditioner  250  is disposed above the polishing pad  220 . The chemical reagent supplying piping  260  is connected to the polishing pad conditioner  250 . The chemical reagent supplying piping  260  is suitable for delivering a chemical reagent to the polishing pad conditioner  250 . The polishing pad conditioner  250  comprises a plurality of diamond brush conditioning heads contacting the polishing pad  220  for removing any rough and uneven felt on the surface of the polishing pad  220  as well as any slurry dregs adhering to the surface of the polishing pad  220 . Furthermore, the chemical reagent also reacts with the slurry dregs adhered to the polishing pad  220  and increases the efficiency of removing slurry dregs. 
     As shown in  FIG. 2 , the splitting piping  280  is connected between the slurry supplying piping  230  and the chemical reagent supplying piping  260 . The splitting piping  280  is suitable for delivering the chemical reagent to the surface of the polishing pad  220  via the chemical reagent supplying piping  260 , the slurry supplying piping  230  and the slurry outlets  212 . 
     In one embodiment, the splitting piping  280  is designed to allow the delivery of chemical reagent to the polishing pad  220  from under the polishing pad  220  for an conditioning operation on the polishing pad  220 . In particular, since the chemical reagent can be supplied from the bottom of the polishing pad  220 , the chemical reagent can dissolve the slurry dregs accumulated near the slurry outlets  212  when passing through the slurry outlets  220  in the polishing platen  210 . Thus, the chemical reagent also serves as a cleaning agent for the slurry outlets  212 . 
     In one embodiment of the present invention, the splitting piping  280  may further comprise a control valve  280   a  and the slurry supplying piping  230  may further comprise another control valve  230   a . When supplying slurry to the polishing pad  220 , the control valve  280   a  is shut while the control valve  230   a  is opened. On the other hand, when supplying chemical reagent to the polishing pad  220 , the control valve  280   a  is opened while the control valve  230   a  is shut. 
     The control valve  280   a  on the splitting piping  280  is used to control the flow of the chemical reagent. The control valve  230   a  on the slurry supplying piping  230  is used to control the flow of the slurry. In one embodiment, when the control valve  280   a  is opened, the control valve  230   a  is shut. In this configuration, the chemical reagent can flow from the chemical reagent supplying piping  260  to the polishing pad conditioner  250  and then drop onto the surface of the polishing pad  220  from above. Also the chemical reagent can be delivered to the surface of the polishing pad  220  from below via the splitting piping  280 , the control valve  280   a , the slurry supplying piping  230  and the slurry outlets  212  for conditioning the polishing pad  220 . 
     Conversely, when the control valve  280   a  is shut and the control valve  230   a  is opened, slurry can flow from a slurry supplying tank  240  to the polishing pad  220  through the slurry supplying piping  230  and the slurry outlets  212  for carrying out a chemical-mechanical polishing operation. 
     Since the chemical-mechanical polishing apparatus  200  in the present embodiment uses a splitting piping  280 , chemical reagent can be delivered to the polishing pad  220  two way from above and below. In the process of providing chemical reagent from below the polishing pad  220 , the chemical reagent also dissolves any slurry particles blocking the slurry outlets  212 . Hence, the slurry can be evenly distributed over the polishing pad  220  to improve polishing performance is subsequent polishing operation. 
       FIG. 2  can also be used to illustrate the method of conditioning a polishing pad  220  according to the present invention. The polishing pad conditioning method is suitable for the aforementioned chemical-mechanical polishing apparatus  200 . 
     After the to-be-polished layer (not shown) on a wafer (not shown) has been polished using the chemical-mechanical polishing apparatus  200 , chemical reagent is supplied to the polishing pad conditioner  250  through the chemical reagent supplying piping  260 . In the meantime, chemical reagent is also supplied to the polishing pad  220  via the splitting piping  280  and the slurry supplying piping  230  and the polishing pad conditioner  250  is activated to condition the surface of the polishing pad  220 . As shown in  FIG. 2 , the polishing pad  220  conditioning method of the present embodiment comprises the following steps. 
     First, chemical reagent is transported from a chemical reagent supplying tank  270  to the polishing pad conditioner  250  via the chemical reagent supplying piping  260  and then the chemical reagent is delivered to the polishing pad  220  from above. At the same time, the control valve  280   a  is opened while the control valve  230   a  is shut so that the chemical reagent can flow to the polishing pad  220  from under via the splitting piping  280 , the slurry supplying piping  230  and the slurry outlets  212 . Because the control valve  230   a  is in a shutdown state, no slurry will go to the polishing pad  220  via the slurry supplying piping  230 . 
     Thereafter, the polishing pad conditioner  250  is used to condition the surface of the polishing pad  220 . The polishing pad conditioner  250  comprises, for example, a plurality of diamond brush conditioning heads contacting the polishing pad  220 . With the chemical reagent delivered to the polishing pad  220  from above and below, slurry dregs and felts adhered to the surface of the polishing pad  220  can be removed. Thus, a certain degree of roughness can be maintained in the polishing pad  220  so that the polishing pad  220  can absorb sufficient slurry to provide a highly stable polishing rate in a subsequent chemical-mechanical polishing operation. 
     As shown in  FIG. 2 , in the aforementioned conditioning steps, the chemical reagent can be delivered to the polishing pad  220  from below and then react with slurry dregs blocking the slurry outlets  212  to facilitate its removal. In other words, the slurry outlets  212  can be kept clean so that the slurry can be evenly distributed on the polishing pad  220  to improve the chemical-mechanical polishing performance of the chemical-mechanical polishing apparatus  200  and extend the working life of the polishing platen  210 . 
     In addition, the aforementioned to-be-polished layer on the wafer is a metallic layer, for example. The material of metallic layer is copper and the corresponding slurry comprises an acid solution and the chemical reagent comprises an acid solution such as a folic acid containing solution. In another embodiment, the material of aforementioned metallic layer is tungsten and the corresponding slurry comprises an acid solution and the chemical reagent comprises a deionized water, for example. In yet another embodiment, the material of metallic layer is tantalum nitride and the corresponding slurry comprises an alkaline solution and the chemical reagent comprises a deionized water, for example. 
     In summary, the chemical-mechanical polishing apparatus and polishing pad conditioning method of the present invention have at least the following advantages. 
     1. The splitting piping of the chemical-mechanical polishing apparatus allows the chemical reagent to remove slurry dregs blocking the slurry outlets when passing through during a polishing pad conditioning operation. Hence, the polishing performance of subsequent polishing operation can be improved. 
     2. Chemical reagent is delivered to the polishing pad from above and below so that a better conditioning performance of the polishing pad is achieved. 
     3. Because the slurry outlets of the chemical-mechanical polishing apparatus are less likely to be blocked, the polishing platen can have a longer life span. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.