Patent Publication Number: US-11654527-B2

Title: Polishing head for use in chemical mechanical polishing and CMP apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of and priority to a Chinese Patent Application No. 201911152824.X filed on Nov. 22, 2019, the entire content of which is incorporated by reference herein. 
     FIELD 
     The present disclosure generally relates to a polishing head for use in chemical mechanical polishing (CMP) and a CMP apparatus having the same. More specifically, the present disclosure relates to a polishing head for use in CMP having air modules to generate an air curtain around its outer surface to prevent slurry loss. 
     BACKGROUND 
     Chemical mechanical polishing or chemical mechanical planarization (CMP) is accomplished by holding the semiconductor wafer in a polishing head against a rotating polishing surface, or otherwise moving the wafer relative to the polishing surface, under controlled conditions of temperature, pressure, and chemical composition. The polishing surface, which may be a planar pad formed of a relatively soft and porous material such as a blown polyurethane, is wetted with a chemically reactive and abrasive aqueous slurry. The aqueous slurry, which may be either acidic or basic, typically includes abrasive particles, reactive chemical agent such as a transition metal chelated salt or an oxidizer, and adjuvants such as solvents, buffers, and passivating agents. Within the slurry, the salt or other agent provides the chemical etching action; whereas the abrasive particles and the polishing pad together provide the mechanical polishing action. 
     During the polishing process, the slurry is continuously supplied to the polishing pad by one or more nozzles. A large amount of the slurry is wasted as the wafer rotates or moves. Usually, only 25% of the slurry contribute to the polishing process, and 75% of the slurry is wasted. 
     Accordingly, there remains a need to provide a CMP apparatus that overcomes the aforementioned problems. 
     SUMMARY 
     In view of above, the present disclosure is directed to a polishing head for use in chemical mechanical polishing (CMP) and a CMP apparatus having the same to improve the use efficiency of slurries. 
     An implementation of the present disclosure is directed to a polishing head for polishing a wafer by a slurry. The polishing head includes a main body and at least two air modules. The main body has a cavity for accommodating the wafer, a main channel, and at least two sub-channels connected to the main channel. The at least two air modules are disposed at an outer surface of the main body. Each of the air modules is respectively connected to one of the sub-channels in the main body and configured to generate an air stream. When the polishing head rotates, the air stream forms an air curtain around the outer surface of the main body. 
     Another implementation of the present disclosure is directed to a chemical mechanical polishing (CMP) apparatus for polishing a wafer by a slurry. The CMP apparatus includes a platen, a slurry nozzle, and a polishing head. The platen has a polishing pad for polishing the wafer. The slurry nozzle is configured to spray the slurry onto the platen. The polishing is configured to hold the wafer and includes a main body and at least two air modules. The main body has a cavity for accommodating the wafer, a main channel, and at least two sub-channels connected to the main channel. The at least two air modules are with respect to the at least two sub-channels and disposed at an outer surface of the main body. Each of the air modules is respectively connected to one of the sub-channels in the main body and configured to generate an air stream. When the polishing head rotates, the air stream forms an air curtain around the outer surface of the main body. 
     Yet another implementation of the present disclosure is directed to a method of polishing a wafer. As shown in  FIG.  5   , the method includes actions S 501  to S 505 . In action S 501 , the wafer is loaded to a chemical mechanical polishing (CMP) apparatus. The CMP apparatus has a polishing head and a platen. The polishing head of the CMP apparatus includes a main body and at least two air modules disposed at an outer surface of the main body. In action S 502 , an air stream is generated by each of the air modules. In action S 503 , the polishing head is rotated to form an air curtain by the air stream around the outer surface of the main body of the polishing head. In action S 504 , a slurry is sprayed to an area between the air curtain and the outer surface of the main body of the polishing head. In action S 505 , the wafer is polished by the slurry on the platen of the CMP apparatus. 
     As described above, the polishing head of the implementations of the present disclosure include at least two air modules disposed at an outer surface of the polishing head. Each of the at least two air modules is configured to generate an air stream. When polishing a wafer, the polishing head is rotated and the air stream forms an air curtain around a side surface of the polishing head. The air curtain formed by the air stream can retain the slurry in an area between the side surface of the polishing head and the air curtain to prevent slurry loss during rotation of the polishing head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG.  1    is a schematic diagram of a CMP apparatus. 
         FIG.  2 A  is a side view of a polishing head of the CMP apparatus of  FIG.  1    according to an implementation of the present disclosure;  FIG.  2 B  is a top view of the polishing head of  FIG.  2 A ;  FIG.  2 C  is a bottom view of the polishing head of  FIG.  2 A . 
         FIG.  3    is a side view of a polishing head of the CMP apparatus of  FIG.  1    according to another implementation of the present disclosure. 
         FIG.  4    is a top view of a polishing head of the CMP apparatus of  FIG.  1    according to another implementation of the present disclosure. 
         FIG.  5    is a flowchart of a method of polishing a wafer according to yet another implementation of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which example implementations of the disclosure are shown. This disclosure may, however, be implemented in many different forms and should not be construed as limited to the example implementations set forth herein. Rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout. 
     The terminology used herein is for the purpose of describing particular example implementations only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” or “has” and/or “having” when used herein, specify the presence of stated features, regions, integers, actions, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, actions, operations, elements, components, and/or groups thereof. 
     It will be understood that the term “and/or” includes any and all combinations of one or more of the associated listed items. It will also be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, parts and/or sections, these elements, components, regions, parts and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, part or section from another element, component, region, layer or section. Thus, a first element, component, region, part or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     The description will be made as to the example implementations of the present disclosure in conjunction with the accompanying drawings in  FIGS.  1  to  3 B . Reference will be made to the drawing figures to describe the present disclosure in detail, wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by same or similar reference numeral through the several views and same or similar terminology. 
     The present disclosure will be further described hereafter in combination with the accompanying figures. 
     Referring to  FIG.  1   , a schematic diagram of a chemical mechanical polishing (CMP) apparatus is illustrated. The CMP apparatus  100  includes a polishing head  130  for polishing a semiconductor wafer W by a slurry  153 . A soft pad  120  is positioned between the polishing head  130  and the wafer W, with the wafer W being held against the soft pad by a partial vacuum or with an adhesive. The polishing head  130  is provided to be continuously rotated by a drive motor  140 , in a direction  141 , and optionally reciprocated transversely in directions  142 . Accordingly, the combined rotational and transverse movements of the wafer W are intended to reduce the variability in the material removal rate across the surface of the wafer W. The CMP apparatus  100  further includes a platen  110 , which is rotatable in a direction  112 . A polishing pad  111  is mounted on the platen  110 . As compared to the wafer W, the platen  110  is provided with a relatively large surface area to accommodate the translational movement of the wafer W on the polishing head  130  across the surface of the polishing pad  111 . A supply tube  151  is mounted above the platen  110  to deliver a stream of polishing slurry  153 , which is dripped onto the surface of the polishing pad  111  from a slurry nozzle  152  of the supply tube  151 . The slurry  153  may be gravity fed from a tank or reservoir (not shown), or otherwise pumped through the supply tube  151 . Alternatively, the slurry  153  may be supplied from below the platen  110  such that it flows upwardly through the underside of the polishing pad  111 . If the particles in the slurry  153  forms agglomeration of undesirable large particles, the wafer surface would be scratched when the wafer W is being polished. Therefore, the slurry  153  needs to be filtered to remove undesirable large particles. Usually, a filter assembly  154  is coupled to the supply tube  151  to separate agglomerated or oversized particles. 
     Referring to  FIGS.  2 A to  2 C , a side view, a top view, and a bottom view of the polishing head  130  of the CMP apparatus  100  of  FIG.  1    according to an implementation of the present disclosure are illustrated. As shown in  FIG.  2 A to  2 C , the polishing head  130  includes a main body  131  and at least two air modules  132 . The main body  131  has a cavity  137  for accommodating the wafer W, a main channel  135 , and at least two sub-channels  136  connected to the main channel  135 . The at least two air modules  132  are disposed at an outer surface of the main body  131 . In this implementation, the polishing head  130  has two air modules  132  disposed correspondingly to two sub-channels  136  of the main body  131 . Each of the air modules  132  is respectively connected to one of the respective sub-channels  136  in the main body  131  and configured to generate an air stream  138 . As shown in  FIGS.  2 B and  2 C , when the polishing head  130  rotates, the air stream  138  forms an air curtain  139  around the outer surface of the main body  131 . 
     The main body  131  has a rotation axis O. The air modules  132  are spaced at substantially equal angular intervals around the rotation axis O of the main body  131 . As shown in  FIGS.  2 B and  2 C , the two air modules  132  may be spaced at 180 degree angular intervals around the rotation axis O of the main body  131 . The main body  131  includes an axial portion  133  and a base portion  134  connected to the axial portion  133 . The base portion  134  has an upper surface  134   a , a side surface  134   b , and a bottom surface  134   c . The cavity  137  of the main body  131  is disposed at the bottom surface  134   c  of the base portion  134 . The main channel  135  is disposed at the axial portion  133  of the main body  131 , and the sub-channels  136  are disposed at the base portion  134  of the main body  131 . Each of the air modules  132  includes an air tube  132   a  and an air nozzle  132   b  connected to the air tube  132   a . The air stream  138  is released downwardly from the air nozzle  132   b  of each of the air modules  132 . In this implementation, each of the sub-channels  136  has an opening  136   a  disposed at the side surface  134   b  of the base portion  134  of the main body  131 . The air tube  132   a  of each of the air modules  132  is connected to the opening  136   a  of each of the sub-channels  136 . The air stream  138  generated by the air modules  132  flows in a direction parallel to the side surface  134   b  of the base portion  134  of the main body  131 . The air curtain  139  formed by the air stream  138  surrounds the side surface  134   b  of the base portion  134 . The air curtain  139  retains the slurry  153  in an area A between the side surface  134   b  of the base portion  134  of the main body  131  and the air curtain  139 . 
     When polishing the wafer W, the slurry  153  is sprayed by the slurry nozzle  152  to the area A between the side surface  134   b  of the base portion  134  of the main body  131  and the air curtain  139 . An air flow is supplied from the main channel  135  and then distributed into each sub-channel  136 . The air flow is released or ejected downwardly from the each of the air nozzle  132   b  to form the air stream  138 . When polishing the wafer W by the slurry  153  on the polishing pad  111 , the polishing head  130  is usually rotated at a rotation rate higher than 100 revolutions per minute (rpm). The air stream  138  generated by each of the air modules  132  forms the air curtain  139  around the side surface  134   b  of the base portion  134  of the main body  131 . Therefore, the slurry sprayed in the air curtain  139  is retained in the area A between the air curtain  139  and the side surface  134   b  of the polishing head  130 . Accordingly, slurry loss during rotation of the polishing head  130  can be greatly reduced. 
     Referring to  FIGS.  3  and  4   , various implementations of the polishing head  130  of the CMP apparatus  100  are illustrated.  FIG.  3    is a side view of the polishing head  130  according to another implementation of the present disclosure.  FIG.  4    is a top view of the polishing head  130  according to yet another implementation of the present disclosure. The polishing head  130  of  FIGS.  3  and  4    is similar to the polishing head  130  of  FIGS.  2 A to  2 C . In  FIG.  3   , each of the sub-channels  136  has an opening  136   a  at the upper surface  134   a  of the base portion  134  of the main body  131 , and the air tube  132   a  of each of the air modules  132  is connected to the opening  136   a  of each of the sub-channels  136 . In  FIG.  4   , the polishing head  130  includes four air modules  132  disposed at the outer surface of the main body  131 . The four air modules  132  are spaced at 90 degree angular intervals around the rotation axis O of the main body  131 . In other implementations, the polishing head  130  may have more air modules than the previous implementations. The details of other components of the polishing head  130  of  FIGS.  3  and  4    can be referred to previous implementations for brevity. 
     According to another implementation, the present disclosure provides a chemical mechanical polishing (CMP) apparatus for polishing a wafer by a slurry. The CMP apparatus of this implementation can be referred to the CMP apparatus  100  of  FIG.  1   . As shown in  FIG.  1   , the CMP apparatus  100  includes a platen  110  having a polishing pad  111  for polishing the wafer W, a slurry nozzle  152 , and a polishing head  130  for holding the wafer W. The slurry nozzle  152  is configured to spray the slurry  153  onto the platen  110 . The polishing head  130  can be referred to  FIGS.  2 A to  4   . The polishing head  130  includes a main body  131  and at least two air modules  132 . The main body  131  has a cavity  137  for accommodating the wafer W, a main channel  135 , and at least two sub-channels  136  connected to the main channel  135 . The at least two air modules  132  are disposed at an outer surface of the main body  131 . Each of the air modules  132  is respectively connected to one of the sub-channels  136  in the main body  131  and configured to generate an air stream  138 . When the polishing head  130  rotates, the air stream  138  forms an air curtain  139  around the outer surface of the main body  131 . The CMP apparatus  100  further includes a drive motor  140  connected to the polishing head  130  to rotate the polishing head  130  in the direction  141 , and optionally reciprocated transversely in the directions  142 . The CMP apparatus  100  may also further includes a supply tube  151  configured to supply the slurry  153  from the slurry nozzle  152 . The details of other components of the CMP apparatus  100  and the polishing head  130  can be referred to the previous implementations. As described above, the polishing head  130  of the CMP apparatus  100  includes at least two air modules  132  disposed at the outer surface of the polishing head  130 . Each of the at least two air modules  132  is configured to generate an air stream  138 . When polishing the wafer W, the polishing head  130  is rotated and the air stream  138  forms an air curtain  139  around a side surface  134   b  of the polishing head  130 . The air curtain  139  can retain the slurry in an area between the side surface  134   b  of the polishing head  130  and the air curtain  139  to prevent slurry loss during rotation of the polishing head  130 . 
     Referring to  FIG.  5   , a flowchart of a method of polishing a wafer according to yet another implementation of the present disclosure is illustrated. As shown in  FIG.  5   , the method S 500  includes actions S 501  to S 506 . In action S 501 , the wafer is loaded to a chemical mechanical polishing (CMP) apparatus having a polishing head and a platen. The polishing head includes a main body and at least two air modules disposed at an outer surface of the main body. The CMP apparatus and the polishing head of the CMP apparatus can be referred to the CMP apparatus  100  and the polishing head  130  of  FIGS.  1  to  4   . The CMP apparatus  100  includes the platen  110  having a polishing pad  111  for polishing the wafer W, a slurry nozzle  152 , and the polishing head  130  for holding the wafer W. The polishing head  130  includes a main body  131  and at least two air modules  132 . The main body  131  has a cavity  137  for accommodating the wafer W, a main channel  135 , and at least two sub-channels  136  connected to the main channel  135 . The at least two air modules  132  are disposed at an outer surface of the main body  131 . 
     In action S 502 , an air stream  138  is generated by each of the air modules  132  of the polishing head. The main body  131  has a rotation axis O. The air modules  132  are spaced at substantially equal angular intervals around the rotation axis O of the main body  131 . The main body  131  includes an axial portion  133  and a base portion  134  connected to the axial portion  133 . The base portion  134  has an upper surface  134   a , a side surface  134   b , and a bottom surface  134   c . The cavity  137  of the main body  131  is disposed at the bottom surface  134   c  of the base portion  134 . The main channel  135  is disposed at the axial portion  133  of the main body  131 , and the sub-channels  136  are disposed at the base portion  134  of the main body  131 . Each of the air modules  132  includes an air tube  132   a  and an air nozzle  132   b  connected to the air tube  132   a . An air flow is supplied from the main channel  135  and then distributed into each sub-channel  136 . The air flow is released or ejected downwardly from the each of the air nozzles  132   b  to form the air stream  138 . The air stream  138  is released or ejected downwardly from the air nozzle  132   b  of each of the air modules  132 . 
     In action S 503 , the polishing head  130  is rotated to form an air curtain  139  by the air stream  138  around the outer surface of the main body  131  of the polishing head  130 . In action S 504 , a slurry  153  is sprayed to an area A between the air curtain  139  and the outer surface of the main body  131  of the polishing head  130 . The slurry  153  is sprayed by the slurry nozzle  152  from a supply tube  151 . In action S 505 , the wafer W is polished by the slurry  153  on the platen  110  of the CMP apparatus  100 . When polishing the wafer W by the slurry  153  on the polishing pad  111  of the platen  110 , the polishing head  130  is usually rotated at a rotation rate higher than 100 revolutions per minute (rpm). The air stream  138  generated by each of the air modules  132  forms the air curtain  139  around the side surface  134   b  of the base portion  134  of the main body  131 . The slurry  153  is sprayed by the slurry nozzle  152  to the area A between the side surface  134   b  of the base portion  134  of the main body  131  and the air curtain  139 . Therefore, the slurry sprayed within the air curtain  139  is retained in the area A between the air curtain  139  and the side surface  134   b  of the polishing head  130 . Accordingly, the slurry loss during rotation of the polishing head  130  can be greatly reduced. 
     As described above, the polishing head of the implementations of the present disclosure include at least two air modules disposed at an outer surface of the polishing head. Each of the at least two air modules is configured to generate an air stream. When polishing a wafer, the polishing head is rotated and the air stream forms an air curtain around a side surface of the polishing head. The air curtain formed by the air stream can retain the slurry in an area between the side surface of the polishing head and the air curtain to prevent slurry loss during rotation of the polishing head. 
     The implementations shown and described above are only examples. Many details are often found in the art such as the other features of a polishing head for use in chemical mechanical polishing and a chemical mechanical polishing (CMP) apparatus having the same. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size, and arrangement of the parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the implementations described above may be modified within the scope of the claims.