Abstract:
A polishing pad according to the invention comprises a pad body having a polishing surface and a support surface and a plurality of hole apertures extending from the polishing surface to the support surface, each of the plurality of apertures having a noncircular shaped opening oriented at a predetermined angle with respect to a radial direction of the polishing pad.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-86087, filed on Mar. 27, 2006, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a polishing pad, a method of polishing and a polishing apparatus for polishing a semiconductor wafer, which are used for a chemical and mechanical polishing (CMP) work in a process of manufacturing semiconductor devices. More particularly, the invention relates to a polishing pad, method of polishing and a polishing apparatus which facilitate a feed flow of a slurry liquid to the polishing pad for a semiconductor wafer.  
         [0004]     2. Description of the Related Art  
         [0005]     In a process of manufacturing semiconductor devices, a CMP work is carried out to polish and flatten dielectrics surface of a wafer. A polishing pad is used for flattening the dielectrics surface. A polishing surface of the polishing pad for use in the CMP work is planar. A surface of the wafer to be polished and the polishing surface of the polishing pad are arranged in parallel to each other. Thus, the wafer surface and the polishing surface are arranged in contact with each other and both are rotated for polishing. Various types of polishing apparatuses are used.  
         [0006]     For example, a polishing pad  100  as shown in  FIG. 19  has a flexible pad  101  and a body pad  102 . The body pad  102  is made of a hard material, foamed urethane, or the like. The body pad  102  has a number of through holes or apertures, which pass through the body pad.  
         [0007]     A polishing pad  110  as shown in  FIG. 20  has a flexible pad  111 , a body pad  112 , through holes  113  and lattice like polishing grooves  114 . The grooves supply and remove an abrasive liquid or slurry and to effectively removes a polishing waste. A polishing pad  112  having polishing grooves  114  formed therein has a high ability to supply and remove the abrasive liquid.  
         [0008]     Therefore, such a pad is advantageous in that polishing amount variations between the central part and the peripheral end part of the wafer are small. The polishing pad is advantageous in that it is easy to peel the wafer from the polishing pad since air can enter between the center of the wafer and the pad through the grooves.  
         [0009]     Variety shapes of through holes are developed to supply and remove a slurry and to effectively remove a polishing waste(refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 2004-71985 and Jpn. Pat. Appln. KOKAI Publication No. 2003-300149).  
         [0010]     However, this type of polishing pad suffers from the following problems. A pad body  102  which has only through holes  103  is not easy to bring forward to feed liquid. On the other hand, a pad body  112  which has only polishing grooves  114  can bring forward to feed liquid into a wafer. However, the depth of the polishing grooves  114  is shorter than the depth of through holes  103 . Therefore, the polishing pad with the pad body  112  is short life.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     It is an object of the present invention to provide a polishing pad which can polish a wafer evenly with small variations of polishing amount. It is an object of the present invention to provide a method of polishing which can polish a wafer evenly with small variations of polishing amount. It is an object of the present invention to provide a polishing apparatus which can polish a wafer evenly with small variations polishing amount. 
    (1)According to one embodiment of the present invention, a polishing pad for polishing an object including a pad body having a polishing surface and a support surface and a plurality of hole apertures extending from the polishing surface to the support surface, each of the plurality of apertures having a noncircular shaped opening oriented at a predetermined angle with respect to a radial direction of the polishing pad.     (2) According to another embodiment of the present invention, a polishing apparatus for polishing an object including a holder mechanism configured to hold the object, a polishing pad configured to be arranged to face the be-polished object hold by the holder mechanism, the polishing pad including a plate-like pad having a polishing surface and a support surface, a drive mechanism to rotate the polishing pad a plurality of hole apertures extending from the polishing surface to the support surface, each of the plurality of apertures having a noncircular shaped opening oriented at a predetermined angle with respect to a radial direction of the polishing pad.     (3) According to another embodiment of the present invention, a method of polishing an object including holding the object and pressing a polishing pad in contact with the object rotating the polishing pad, the polishing pad including a pad body having a polishing surface and a support surface and a plurality of hole apertures extending from the polishing surface to the support surface, each of the plurality of apertures having a noncircular shaped opening oriented at a predetermined angle with respect to a radial direction of the polishing pad.   
 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0015]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0016]      FIG. 1  is a schematic view of a polishing apparatus having a polishing pad in accordance with one embodiment of the invention.  
         [0017]      FIG. 2  is a plan view showing the polishing pad in accordance with one embodiment of the invention.  
         [0018]      FIG. 3  is a plan view showing through holes of the polishing pad in accordance with one embodiment of the invention.  
         [0019]      FIG. 4  is a graph showing a relationship between the polishing rate and the proportion of major axis of the through hole in accordance with one embodiment of the invention.  
         [0020]      FIG. 5  is a plan view showing a polishing pad in accordance with another embodiment of the invention.  
         [0021]      FIG. 6  is an explanatory view showing positional relation of the through hole in  FIG. 5   
         [0022]      FIG. 7  is an explanatory view showing relation of polishing rate in accordance with another embodiment of the invention.  
         [0023]      FIG. 8  is a plan view showing a polishing pad in accordance with another embodiment of the invention.  
         [0024]      FIG. 9  is an explanatory view showing positional relation of the through hole in  FIG. 8 .  
         [0025]      FIG. 10  is an explanatory view showing a relation of polishing rate and a proportion of major axis to minor axis of the through hole in accordance with another embodiment of the invention.  
         [0026]      FIG. 11  is a plan view showing a polishing pad in accordance with another embodiment of the invention.  
         [0027]      FIG. 12  is a plan view showing a polishing pad in accordance with another embodiment of the invention.  
         [0028]      FIG. 13  is an explanatory view showing positional relation of a through hole and a central of the polishing pad in accordance with another embodiment of the invention.  
         [0029]      FIG. 14  is an explanatory view showing relation of polishing rate and angle in accordance with another embodiment of the invention.  
         [0030]      FIG. 15  is a plan view showing a polishing pad in accordance with another embodiment of the invention.  
         [0031]      FIG. 16  is a plan view showing a polishing pad in accordance with another embodiment of the invention.  
         [0032]      FIG. 17  is an explanatory view showing positional relation of a through hole and a central of the polishing pad in accordance with another embodiment of the invention.  
         [0033]      FIG. 18  is a plan view showing a polishing pad in accordance with another embodiment of the invention.  
         [0034]      FIG. 19  is a cross sectional view showing a polishing pad.  
         [0035]      FIG. 20  is a cross sectional view showing a polishing pad. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]      FIG. 1  is a structural view showing a polishing apparatus  100  set up a polishing pad  10 , which is a first embodiment of the present invention.  FIG. 2  is a plan view showing the polishing pad  10 .  FIG. 3  is a plan view showing through holes  20  which is provided on the polishing pad  10 . X is a rotating center on the polishing pad  10 , F is a flowing direction of abrasive liquid and P is a rotating direction of the polishing pad  10 .  
         [0037]     The polishing apparatus  100  has the polishing pad  10 , a holder mechanism  110  providing a wafer w and a rotary drive mechanism  120  which rotates the polishing pad  10 , as shown in  FIG. 1 .  
         [0038]     The polishing pad  10  is laminated with a soft pad  11  and a pad body  12 . The pad body  12  is made of hard resin such as formed polyurethane or urethane.  
         [0039]     The pad body  12  is provided with the through holes  20 . The through holes  20  are provided from a polishing surface  12   a  to a support surface  12   b,  in other words, in the thickness direction of the pad body  12 . The through holes  20  formed by such as a punching process or a nesting block.  
         [0040]     A predetermined number of the through holes  20  are provided in approximately a concentric fashion on the polishing body  12 , as shown in the embodiment illustrated in  FIG. 2 . The through holes  20  is provided in approximately a concentric fashion with respect to the rotating center X on the polishing pad  10  when a to-be-polished object is polished, too. The through holes  20  are noncircular shaped openings. The through holes  20  are provided in a predetermined angle with respect to a radial direction. It is better that all of the through holes  20  are provided in the same predetermined angle. However, if there is a positive effect, all of the through holes  20  don&#39;t need to be same angle.  
         [0041]     The through holes  20  may be elliptical, as shown in  FIG. 3 . The elliptical shape of the holes has a minor axis a and a major axis b. The rotating center X is provided on a line extending from the minor axis.  
         [0042]     In one embodiment, the through holes  20  may be provided at 1-10 per 1 cm2. One of a dimension of the through holes  20  is 1-6 mm2. A surface ratio of the through holes  20  with respect to the surface area of the pad body  12  may be 1-60 percent.  
         [0043]     The through holes  20  are provided along a line on which the abrasive liquid flows or travels. It is easy to flow out abrasive liquid which is in the through holes  20 . As a result, it promotes to feed and exhaust the abrasive liquid, and a polishing rate rises. And a life of the polishing pad  10  does not change compared with a life of using only prior through holes.  
         [0044]     A polishing rate rises to increase b/a (a rate of major axis for a minor axis), as shown in  FIG. 4 . For example, in case of b/a=1.2, a polishing rate rises about 10 percent compared with prior through holes (b/a=1).  
         [0045]     According to the embodiment of the polishing pad  10 , it can promote to feed and exhaust the abrasive liquid. And the polishing rate can rise.  
         [0046]      FIG. 5  is a plan view showing a polishing pad  10 A which is a second embodiment of the present invention.  FIG. 6  is a showing relationship between the through holes  20  and the rotating center X. In  FIG. 5  and  FIG. 6 , the same functional parts showing in  FIG. 2  and FIG.  3  are given the same number and overlapping explanation is skipped.  
         [0047]     For the polishing pad  10 A, which is one embodiment of the present invention, the major axis of the through holes  20  is provided at a predetermined angle θ with respect to the radial direction R. The through holes  20  can promote to feed and exhaust the abrasive liquid with centrifugal force.  
         [0048]      FIG. 7  shows a change in polishing rate when angle θ is changed from 0 degree to 90 degree. When angle θ is 90 degree in  FIG. 2 , the minor direction is accorded with the diameter direction R. When angle θ is from 40 degree to 80 degree, the polishing rate is maximum. The maximum polishing rate is twice as the polishing rate in  FIG. 2 . Angle θ of the maximum polishing rate change according to rotary speed of a polishing pad.  
         [0049]     The polishing pad  10 A can promote to feed and exhaust the abrasive liquid and improve the polishing rate.  
         [0050]      FIG. 8  is a plan view showing a polishing pad  10 B which is a third embodiment of the present invention.  FIG. 9  shows relationship between the through holes  30  and the rotating center X of the polishing pad  10 B. In  FIG. 8  and  FIG. 9 , the same functional parts showing in  FIG. 2  and  FIG. 3  are given the same number and overlapping explanation is skipped.  
         [0051]     On the polishing pad  10 B of the embodiment of the present invention, the through holes  30  are provided. The through holes  30  are teardrop shape which shape is wider down stream area than up stream side.  
         [0052]     A polishing rate rises to increase d/c (a rate of major axis for a minor axis), as shown in  FIG. 10 . For example, in case of d/c=1.2, a polishing rate rises about 5 percent compared with prior through holes (b/a=1).  
         [0053]      FIG. 11  is a plan view showing a polishing pad  10 C which is a forth embodiment of the present invention. In  FIG. 11 , the same functional parts showing in  FIG. 8  are given the same number and overlapping explanation is skipped.  
         [0054]     On the polishing pad  10 C of the embodiment of the present invention, a down stream side of the through holes  30  is angled outwardly, away from the center of the pad. In this arrangement, the through holes  30  can promote to supply and drain the abrasive liquid by a centrifugal force.  
         [0055]      FIG. 12  is a plan view showing a polishing pad  10 D which is a fifth embodiment of the present invention.  FIG. 13  shows relationship between the through holes  40  and the rotating center X of the polishing pad  10 B. In  FIG. 12  and  FIG. 13 , the same functional parts showing in  FIG. 2  and  FIG. 3  are given the same number and overlapping explanation is skipped.  
         [0056]     On the polishing pad  10 D of the embodiment of the present invention, through holes  40  are provided. The through holes  40  are teardrop shape which shape is gradually wider down stream area than up stream side. Down stream area of through holes  40  are provided to be leaned φ degree to inner circumference configuration.  
         [0057]     As shown in  FIG. 14 , a polishing rate rises to adjust φ degree. For example, when φ is provided more than 20 degree, a polishing rate rises about 5 percent compared with through holes  30  which are teardrop shape.  
         [0058]      FIG. 15  is a plan view showing a polishing pad  10 E which is a sixth embodiment of the present invention. In  FIG. 15 , the same functional parts showing in  FIG. 12  are given the same number and overlapping explanation is skipped.  
         [0059]     On the polishing pad  10 E of the embodiment of the present invention, the through holes  40  are provided to be leaned for circumferential direction. In other words, a down stream area of the abrasive liquid, a side of the through holes  30  provided to be out side direction on the polishing pad  10 E.  
         [0060]     The through holes  40  can nurture to feed and exhaust the abrasive liquid with centrifugal force.  
         [0061]      FIG. 16  is a plan view showing a polishing pad  10 F which is a seventh embodiment of the present invention.  FIG. 17  is a showing relationship between the through holes  50  and the rotating center X of the polishing pad  10 B.  
         [0062]     In  FIG. 16  and  FIG. 17 , the same reference numeral as in  FIG. 2  and  3  are used for the same functional parts, and their explanations are omitted.  
         [0063]     On the polishing pad  10 F of the embodiment of the present invention, the through holes  50  are provided. The through holes  50  are teardrop shape having a down stream area gradually wider than an up stream side. Down stream area of through holes  50  is angled outwardly at φ degree with respect to the up stream side. Outer configuration is defined as below zero.  
         [0064]     A polishing rate rises to adjust φ degree. For example, when φ is provided more than −20 degree, a polishing rate rises about 5 percent compared with through holes  30  which are teardrop shape.  
         [0065]      FIG. 18  is a plan view showing a polishing pad  10 G which is a eighth embodiment of the present invention.  
         [0066]     In  FIG. 18 , the same functional parts showing in  FIG. 16  are given the same number and overlapping explanation is skipped.  
         [0067]     In one embodiment, for the polishing pad  10 G, the through holes  50  are provided to be leaned for circumferential direction. In other words, the through holes  50  are provided to be leaned to out side direction on down stream area of the abrasive liquid. The through holes  50  can nurture to feed and exhaust the abrasive liquid with centrifugal force.  
         [0068]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.