Patent Publication Number: US-2019193238-A1

Title: Wafer polishing pad and method of wafer polishing using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. nonprovisional application claims priority under 35 U.S.C § 119 to Korean Patent Application No. 10-2017-0180750 filed on Dec. 27, 2017, in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relate to a polishing pad, and more particularly, to a wafer polishing pad and a method of wafer processing using the wafer polishing pad. 
     DISCUSSION OF THE RELATED ART 
     An integrated circuit is generally formed by successively disposing conductors, semiconductors, and/or insulators on a wafer. After each layer is disposed, the layer is etched to define the circuit. As layers are successively disposed and etched, the wafer gradually becomes rough on its exposed surface. To correct for this roughness, the wafer may be periodically planarized to flatten the exposed surface of the wafer. A chemical mechanical polishing process may be employed in planarizing the wafer. The chemical mechanical polishing process may use a polishing pad to polish the wafer. 
     SUMMARY 
     A wafer polishing pad includes a first pad having a first surface configured to receive a platen. A protrusion is disposed on the first surface of the first pad. The protrusion is disposed on an edge region of the first pad in a plan view such that a side surface of the protrusion makes contact with a side surface of the platen when the first pad is disposed on the platen. 
     A wafer polishing pad includes a top surface including a groove. A first bottom surface opposite to the top surface corresponds to a central region of the polishing pad. A second bottom surface opposite to the top surface corresponds to an edge region of the polishing pad. The second bottom surface is located at a lower level than that of the first bottom surface. 
     A wafer polishing method includes preparing a polishing pad comprising a first pad and a protrusion. The protrusion is disposed on an edge region of a first surface of the first pad. The polishing pad is placed on a platen such that the first surface of the first pad faces the platen. A wafer is polished using the polishing pad. Placing the polishing pad on the platen includes causing the protrusion of the polishing pad to make contact with a sidewall of the platen. 
     A wafer polishing pad includes a polishing surface configured to mechanically polish a wafer. A receiving surface, opposite to the polishing surface, is configured to make contact with a top surface of a platen. A ring is disposed on the receiving surface and the ring is configured to make contact with a side surface of the platen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the present disclosure and many of the attendant aspects thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1A  is a plan view illustrating a polishing pad according to exemplary embodiments of the present disclosure; 
         FIG. 1B  is a plan view illustrating grooves of a polishing pad according to exemplary embodiments of the present disclosure; 
         FIG. 1C  is a cross-sectional view taken along line I-II of  FIG. 1A ; 
         FIG. 2  is a cross-sectional view illustrating a polishing pad according to exemplary embodiments of the present disclosure; 
         FIG. 3A  is a plan view illustrating a polishing pad according to exemplary embodiments of the present disclosure; 
         FIG. 3B  is a cross-sectional view taken along line I-II of  FIG. 3A ; 
         FIG. 3C  is a cross-sectional view illustrating an adhesive layer attaching method according to exemplary embodiments of the present disclosure; 
         FIG. 4  is a flow chart illustrating a wafer polishing method according to exemplary embodiments of the present disclosure; 
         FIG. 5  is a perspective view illustrating a wafer polishing method according to exemplary embodiments of the present disclosure; and 
         FIG. 6  is a cross-sectional view illustrating a polishing pad associated with a platen in accordance with exemplary embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In describing exemplary embodiments of the present disclosure illustrated in the drawings, specific terminology is employed for sake of clarity. However, the present disclosure is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents which operate in a similar manner. In the specification and the various figures, like reference numerals may indicate like components. 
     Exemplary embodiments of the present invention may utilize a wafer polishing pad and a wafer polishing method using the same. 
       FIG. 1A  is a plan view illustrating a polishing pad according to exemplary embodiments of the present disclosure.  FIG. 1B  is a plan view illustrating grooves disposed on a polishing pad, according to exemplary embodiments of the present disclosure, showing a top surface of the polishing pad.  FIG. 1C  is a cross-sectional view taken along line I-II of  FIG. 1A . 
     Referring to  FIGS. 1A to 1C , a polishing pad  10  may include a first pad  100  and a protrusion  300 . The first pad  100  may have a plurality of pores at least partially penetrating the first pad  100 . The first pad  100  may include, for example, a polymer such as polyurethane. The pores of the first pad  100  may receive slurry. The slurry may be used for chemically and mechanically polishing a polishing target, using the first pad  100 . The polishing target may be a wafer. 
     The first pad  100  may have a first surface  100   a  and a second surface  100   b  opposite to the first surface  100   a . The second surface  100   b  of the first pad  100  may correspond to a top surface of the polishing pad  10  while the first surface  100   a  of the first pad  100  may correspond to a bottom surface of the polishing pad. The second surface  100   b  of the first pad  100  may serve as a polishing surface. For example, the second surface  100   b  of the first pad  100  may make contact with and polish the polishing target. The second surface  100   b  of the first pad  100  may be relatively rough, for example, the second surface  100   b  may be rougher than the first surface  100   a . The first pad  100  may have a uniform thickness. For example, central and edge regions of the first pad  100  may have the same or similar maximum thickness. The second surface  100   b  of the first pad  100  may be straight and unbent. For example, the second surface  100   b  of the first pad  100  may have central and edge regions whose respective topmost portions are located at substantially the same level. The edge region of the second surface  100   b  of the first pad  100  may indicate a zone overlapped with the protrusion  300 . 
     A plurality of grooves  210  may be disposed on the second surface  100   b  of the first pad  100 . As illustrated in  FIG. 1B , one or more of the plurality of grooves  210  may extend radially from a center of the polishing pad  10  toward an edge of the polishing pad  10 . Others of the plurality of grooves  210  may be arranged in concentric circles. However, the present invention does not necessarily have this particular geometric configuration of grooves  210 . For example, the grooves  210  may have spiral shapes. The planar shape of the grooves  210  may be arranged in various ways, all within the scope of the present disclosure. When a polishing process is performed, the grooves  210  may act as slurry paths through which the slurry may travel. 
     The protrusion  300  may be disposed on the first surface  100   a  of the first pad  100 . The first surface  100   a  of the first pad  100  may be relatively flat. When viewed in plan as illustrated in  FIG. 1A , the protrusion  300  may overlap with and extend up from an edge region of the first surface  100   a  of the first pad  100 . The protrusion  300  may have a closed loop shape such as a ring shape. The protrusion  300  may expose a central region of the first surface  100   a  of the first pad  100 . The protrusion  300  may have a height H equal to or greater than about 1 mm, for example, ranging from about 1 mm to about 100 mm, as may be seen in  FIG. 1C . The protrusion  300  may have a bottom surface  300   a  at a different level from that of the first surface  100   a  of the first pad  100 . For example, the bottom surface  300   a  of the protrusion  300  may be disposed at a lower level than that of the first surface  100   a  of the first pad  100 . The protrusion  300  may have a width W ranging from about 2 mm to about 5 mm. 
     For example, the protrusion  300  and the first pad  100  may be integrally formed so as to constitute a single unitary body. The protrusion  300  and the first pad  100  may be connected to each other without a boundary, and may include the same material. The protrusion  300  may alternatively be formed by attaching a separate structure (e.g., a preliminary protrusion) onto the first surface  100   a  of the first pad  100 . In this case, the protrusion  300  and the first pad  100  may include the same or different materials, and an adhesion may be used to attach the first pad  100  and the protrusion  300 . The protrusion  300  may include a polymer, but the protrusion  300  may be formed of another material. 
     An adhesive layer  500  may further be disposed on the first surface  100   a  of the first pad  100 . The first pad  100  may thus have the adhesive layer  500  attached onto an area of the first surface  100   a  that is not covered with the protrusion  300 . The adhesive layer  500  may have a thickness that is less than the height H of the protrusion  300 . The bottom surface  300   a  of the protrusion  300  may be located at a lower level than that of a bottom surface of the adhesive layer  500 . The adhesive layer  500  may further extend along an inside surface  300   c  (e.g. inside facing sidewall) of the protrusion  300 . The adhesive layer  500  may include a polymer. 
       FIG. 2  is a cross-sectional view taken along line I-II of  FIG. 1A , showing a polishing pad according to exemplary embodiments of the present invention. It may be assumed that elements that are not described in detail below are at least similar to corresponding elements described above. 
     Referring to  FIG. 2 , a polishing pad  11  may include a protrusion  300 , a first pad  100 , and a second pad  200 . The first pad  100  and the protrusion  300  may be at least similar to corresponding elements discussed above with reference to  FIGS. 1A and 1B . The polishing pad  11  may have a first bottom surface and a second bottom surface respectively corresponding to a central region and an edge region in a plan view. The first bottom surface may correspond to the first surface  100   a  of the first pad  100 , and the second bottom surface may correspond to the bottom surface  300   a  of the protrusion  300 . The second bottom surface may be located at a lower level than that of the first bottom surface. The first pad  100  may be covered with the adhesive layer  500  on its first surface  100   a  (e.g., the first bottom surface) exposed by (e.g. not covered by) the protrusion  300 . The second surface  100   b  of the first pad  100  may have central and edge regions whose respective topmost portions are located at the same or similar level. Differently from that shown  FIGS. 1B and 1C , the second surface  100   b  of the first pad  100  might not serve as a polishing surface, and no grooves  210  are disposed in the first pad  100 . 
     The second pad  200  may be disposed on the first pad  100 . The second pad  200  may have a plurality of pores at least partially penetrating the second pad  200 . The second pad  200  may include, for example, a polymer such as polyurethane. The second pad  200  may have a first surface facing the first pad  100  and a second surface  200   b  opposite to the first surface. The second surface  200   b  of the second pad  200  may correspond to a top surface of the polishing pad  11 . The second surface  200   b  of the second pad  200  may serve as a polishing surface. A plurality of grooves  210  may be disposed on the second surface  200   b  of the second pad  200 . The grooves  210  may have planar shapes and may be at least similar to the grooves  210  discussed above with reference to  FIGS. 1B and 1C . Central and edge regions of the second pad  200  may have substantially the same maximum thickness as each other. The second surface  200   b  of the second pad  200  may have central and edge regions whose respective topmost portions are located at substantially the same level. 
     An adhesive pattern  150  may be interposed between the first pad  100  and the second pad  200 . The second pad  200  may be attached through the adhesive pattern  150  to the first pad  100 . The adhesive pattern  150  may include an insulating polymer. Central and edge regions of the adhesive pattern  150  may have substantially the same maximum thickness as each other. 
       FIG. 3A  is a plan view illustrating a polishing pad according to exemplary embodiments of the present disclosure.  FIG. 3B  is a cross-sectional view taken along line I-II of  FIG. 3A . It may be assumed that elements that are not described in detail below are at least similar to corresponding elements described above. 
     Referring to  FIGS. 3A and 3B , a polishing pad  12  may include a first pad  100 , a second pad  200 , and a protrusion  300  disposed on the first pad  100 . The first pad  100 , the second pad  200 , and the protrusion  300  may each be substantially the same as corresponding elements discussed above with reference to  FIGS. 1A to 1C and 2 . It is to be understood, however, that the adhesive pattern  150  and the second pad  200  are optional elements and may be omitted without departing from the scope of the present disclosure. As illustrated in  FIGS. 1B and 1C , the grooves  210  may be disposed in the first pad  100 . The protrusion  300  may have an inside surface  300   c  and an outside surface  300   d  opposite to each other. The inside and outside surfaces  300   c  and  300   d  of the protrusion  300  may extend in a direction intersecting the first surface  100   a  of the first pad  100 . 
     A plurality of vent grooves  310  may be disposed in the protrusion  300 . The vent grooves  310  may be disposed on and may penetrate the bottom surface  300   a  of the protrusion  300 . As illustrated in  FIG. 3B , the vent grooves  310  may have floor surfaces  310   a  at substantially the same level as that of the first surface  100   a  of the first pad  100 . The floor surfaces  310   a  of the vent grooves  310  may be connected to the first surface  100   a  of the first pad  100 . When viewed in plan, as illustrated in  FIG. 3A , the vent grooves  310  may extend from the inside surface  300   c  of the protrusion  300  toward the outside surface  300   d  of the protrusion  300 . For example, the vent grooves  310  may penetrate the inside and outside surfaces  300   c  and  300   d  of the protrusion  300 . Alternatively, the vent grooves  310  may penetrate the inside surface  300   c  of the protrusion  300 , but not the outside surface  300   d  of the protrusion  300 . The number and planar shapes of the vent grooves  310  is not limited to the arrangements shown, and various different arrangements may be used, within the scope of the present disclosure. 
     The protrusion  300  may be formed on the first pad  100 , and then the protrusion  300  may be partially removed to form the vent grooves  310 . According to an exemplary embodiment of the present disclosure, the formation of the vent grooves  310  may include preparing a plurality of preliminary protrusions and attaching the preliminary protrusions onto the first surface  100   a  of the first pad  100  so as to be spaced apart from each other. In this case, the protrusion  300  may include a plurality of sub-protrusions spaced apart from each other, and the vent grooves  310  may be disposed between each of the plurality of sub-protrusions. 
     A mark  400  may further be disposed on the bottom surface  300   a  of the protrusion  300 . The mark  400  may be a character or figure displayed on the bottom surface  300   a  of the protrusion  300 . For example, the mark  400  may be formed by attaching a pattern onto the bottom surface  300   a  of the protrusion  300 . Alternatively, the mark  400  may be a recession formed within the bottom surface  300   a  of the protrusion  300 . A planar arrangement of the mark  400  is not limited to that shown, and various different arrangements are within the scope of the present disclosure. 
     The first pad  100  may include an adhesive layer  500  on its first surface  100   a  exposed by (e.g. not covered by) the protrusion  300 . The adhesive layer  500  may further cover the inside surface  300   c  of the protrusion  300 . An attaching process of the adhesive layer  500  and functions of the vent grooves  310  are described in greater detail below. 
       FIG. 3C  is a cross-sectional view taken along line I-II of  FIG. 3A , showing a method for attaching an adhesive layer according to exemplary embodiments of the present disclosure. It may be assumed that elements that are not described in detail below are at least similar to corresponding elements described above. 
     Referring to  FIGS. 3A and 3C , the adhesive layer  500  may be disposed onto the first surface  100   a  of the first pad  100 . In the process of attaching the adhesive layer  500 , as indicated by an arrow in  FIG. 3C , air may flow into the vent grooves  310  from between the adhesive layer  500  and the first pad  100 . Air bubbles may then be reduced or prevented from being formed between the adhesive layer  500  and the first pad  100 . The adhesive layer  500  may be sufficiently attached to the first pad  100 . The mark  400  may signify an attachment direction in the process of attaching the adhesive layer  500 . The attachment direction of the adhesive layer  500  may intersect the directions of extension of the vent grooves  310 . Therefore, in the process of attaching the adhesive layer  500 , air may be easily discharged through the vent grooves  310  to the outside. 
     A wafer polishing method according to exemplary embodiments of the present disclosure is described in detail below. 
       FIG. 4  is a flow chart illustrating a wafer polishing method according to exemplary embodiments of the present disclosure.  FIG. 5  is a perspective view illustrating a wafer polishing method according to exemplary embodiments of the present disclosure.  FIG. 6  is a cross-sectional view illustrating a polishing pad associated with a platen. It may be assumed that elements that are not described in detail below are at least similar to corresponding elements described above. 
     Referring to  FIG. 4 , one of the polishing pads  10 ,  11 , and  12  including the protrusion  300  may be prepared (S 10 ). For example, the polishing pad  10  discussed with reference to  FIGS. 1A to 1C , the polishing pad  11  discussed with reference to  FIG. 2 , or the polishing pad  12  discussed with reference to  FIGS. 3A and 3B  may be prepared. The first pad  100  may include the adhesive layer  500  attached onto its first surface  100   a  exposed by (e.g. not covered by) the protrusion  300 . For example, the attachment of the adhesive layer  500  may be performed at least similarly to that discussed above with reference to  FIG. 3C . For convenience of description, a wafer polishing method using the polishing pad  11  of  FIG. 2  will be described. According to exemplary embodiments of the present disclosure, a top surface of the polishing pad  11  may denote the second surface  200   b  of the second pad  200 . When the polishing pad  10  of  FIGS. 1A to 1C  is used, the top surface of the polishing pad  11  may denote the second surface  100   b  of the first pad  100 . 
     Referring to  FIG. 5 , a polishing apparatus may be prepared. The polishing apparatus may include a platen  1000 , a wafer carrier  2000 , a slurry supply  3000 , and a pad conditioner  4000 . The platen  1000  may have, for example, a cylindrical shape. The platen  1000  may receive power from a motor and the platen  1000  may be caused to rotate around its rotational axis. The rotational axis may be perpendicular to a top surface of the platen  1000 . 
     Referring to  FIGS. 4, 5, and 6 , the polishing pad  11  may be placed on the top surface of the platen  1000  so as to cause the first surface  100   a  of the first pad  100  to face the top surface of the platen  1000  (S 20 ). The polishing pad  11  may be attached through the adhesive layer  500  to the platen  1000 . As illustrated in  FIG. 6 , the polishing pad  11  may have a diameter A 1  greater than a diameter A 2  of the platen  1000 . The first pad  100  may have a diameter on its first surface  100   a  (e.g., the first bottom surface) exposed by (e.g. not covered by) the protrusion  300 , and the diameter of the first surface  100   a  may be the same as or greater than the diameter A 2  of the platen  1000 . The protrusion  300  may be disposed on a sidewall  1000   d  of the platen  1000 . The polishing pad  11  may then be precisely aligned with the platen  1000 . For example, in a plan view, a central point of the polishing pad  11  may be aligned with a central point of the platen  1000 . In addition, the polishing pad  11  and the platen  1000  may be aligned with each other at high speed to reduce process time. The protrusion  300  may more rigidly fix the polishing pad  11  to the platen  1000 . 
     The polishing pad  11  may be used to polish a wafer WF (S 30 ). In some exemplary embodiments of the present disclosure, the wafer WF may be prepared. The wafer carrier  2000  may use vacuum pressure to hold the wafer WF so as to cause a polishing target surface of the wafer WF to face the polishing pad  11 . The wafer carrier  2000  may be driven to move up and down by an elevation unit. The wafer carrier  2000  may move downward to contact with the polishing pad  11  when a polishing process is performed. The wafer carrier  2000  may rotationally move to rotate the wafer WF during the polishing process. 
     The slurry supply  3000  may provide slurry onto the top surface of the polishing pad  11 . A material of the slurry may be determined based on a kind and material of the polishing target surface of the wafer WF. The slurry may chemically polish the polishing target surface of the wafer WF, while contacting the polishing target surface of the wafer WF. For example, the polishing target surface of the wafer WF may change into an easily removable state due to reaction with the slurry. 
     The polishing pad  11  may be supported by and may rotate together with the platen  1000  during the polishing process. As discussed above, the pores of the first pad  100  or of the second pad  200  may receive the slurry. The polishing target surface of the wafer WF and the top surface of the polishing pad  11  may abrade against each other to mechanically polish the polishing target surface of the wafer WF. The grooves  210  may serve as paths for the slurry and polishing residues. When the central point of the polishing pad  11  is misaligned with the central point of the platen  1000 , the slurry in the grooves  210  may move unintentionally. In some exemplary embodiments of the present disclosure, since the polishing pad  11  and the platen  1000  are accurately aligned with each other due to the protrusion  300 , when the platen  1000  moves in rotary motion, the slurry may be evenly distributed in the grooves  210  and slurry residues may be satisfactorily discharged/removed from the grooves  210 . As a result, the wafer WF may be evenly polished on its polishing target surface. 
     The pad conditioner  4000  may be installed adjacent to the platen  1000 . The pad conditioner  4000  may move rotationally and reciprocally. The pad conditioner  4000  may contact the top surface of the polishing pad  11  and maintain an even surface roughness of the top surface of the polishing pad  11 . Therefore, even though the polishing process is performed for a long time, the wafer WF may be satisfactorily polished on its polishing target surface. 
     When the diameter A 1  of the polishing pad  11  is the same as or less than the diameter A 2  of the platen  1000 , the pad conditioner  4000  may come into contact with the platen  1000  (e.g., with an edge portion of the platen  1000 ) during the operation of the pad conditioner  4000 . In this case, the pad conditioner  4000  and/or the platen  1000  may suffer from damage. In some exemplary embodiments of the present disclosure, the diameter A 1  of the polishing pad  11  may be greater than the diameter A 2  of the platen  1000 . For example, the diameter A 1  of the polishing pad  11  may be approximately 5 to 10 mm larger than the diameter A 2  of the platen  1000 . The pad conditioner  4000  and the platen  1000  may accordingly be prevented from colliding against each other. 
     When the diameter A 1  of the polishing pad  11  is greater than the diameter A 2  of the platen  1000 , an edge portion of the polishing pad  11  might not be supported by the platen  1000 . When no protrusion  300  is provided, edge portions of the first and second pads  100  and  200  may bend down lower than central portions of the first and second pads  100  and  200 . For example, the edge portions not being supported by the platen  1000  may tend to bend inwardly toward the platen  1000 . The top surface of the polishing pad  11  may thus be bent. The bending portion of the top surface of the polishing pad  11  may be excessively abraded by the pad conditioner  4000 , with the result that the polishing pad  11  may decrease in life span. In some exemplary embodiments of the present disclosure, the polishing pad  11  may include the protrusion  300 . The protrusion  300  may be disposed on the edge portion of the first pad  100 . Hence, the edge portion of polishing pad  11  may be supported and this support may prohibit the first pad  100  from bending down. When the height H of the protrusion  300  is less than 1 mm, it may be unlikely that the protrusion  300  sufficiently prevents the bending of the polishing pad  11 . In some exemplary embodiments of the present disclosure, the height H of the protrusion  300  may fall within a range equal to or greater than 1 mm, and thus the polishing pad  11  may be sufficiently prevented from bending. The polishing pad  11  may accordingly be prevented from being excessively abraded on its top surface. Thus, the polishing pad  11  may increase in life span. 
     According to exemplary embodiments of the present disclosure, a polishing pad may include a protrusion. The polishing pad may be disposed on the top surface of a platen. The protrusion may be disposed on the sidewall of the platen. The protrusion may accurately and quickly align the polishing pad with the platen. The process time may then decrease. The protrusion may rigidly fix the polishing pad to the platen. 
     The protrusion may prevent the polishing pad from bending down on the platen. The protrusion may suppress excessive abrasion of the polishing pad, and as a result, the polishing pad may increase in life span. 
     Exemplary embodiments described herein are illustrative, and many variations can be introduced without departing from the spirit of the disclosure or from the scope of the appended claims. For example, elements and/or features of different exemplary embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.