Patent Publication Number: US-8123597-B2

Title: Polishing pad

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a polishing pad, and more particularly, to a polishing pad with two groove patterns. 
     2. Description of the Prior Art 
     Electrical chips are formed by deposition of various laminate materials, for example, a silicon wafer is one of the substrates of laminate materials. Whenever a new laminate is deposited, a polishing or scrapping step is often needed for removing excessive laminate materials to planarize the chip or to achieve other purposes. Such process of polishing is generally called chemical mechanical polishing (CMP). Since chips are formed by deposition of different thin film laminates, the CMP step needs to be performed for multiple times for evenly removing excessive laminate materials from the surface of a chip to achieve the purpose of planarization. 
     And usually when the CMP step is performed, chemical slurry is led in between the chip and the polishing pad for generating chemical reaction between the deposited thin film laminates and the chemical slurry or for generating mechanical reaction between the deposited thin film laminates and the particles in the chemical slurry to remove part of excessive thin film laminates on the surface of chip. However, the slurry existing between the polishing pad and the chip makes it easy for the polishing pad and the chip to become fully attached to each other, which thus causes disappearance of the force of friction between the polishing pad and the chip. Therefore, in order to achieve better polishing effect with the CMP step, the most common practice at present is to install groove on the surface of the polishing pad not only for increasing force of friction between the polishing pad and the chip but also for ensuring that the slurry is evenly distributed on the surface of the polishing pad and for letting polishing particles suspended in the slurry and the scraps to flow out through the groove. 
     In prior art, many patents make improvements particularly on the pattern of groove installed on the surface of polishing pad. Taking Taiwan patent No. I250572 for one example, referring to  FIG. 1A , groove  11  is formed on the surface side of polishing pad  10 , the pattern of which being selected from the group consisting of ring-shape, grid-shape, and helix-shape,  FIG. 2A  being a sectional view drawn according a-a′ sectional line in  FIG. 1A ; taking Taiwan patent No. 200744786 for another example, referring to  FIG. 2 , the polishing pad  20  includes two sets of grooves on its surface, one set being the first kind of grooves  21  that intersect a single virtual direct line extending from center of polishing pad  20  to surround, the set of groove  21  does not intersect each other, the other set being the second kind of grooves  22  that extend from central part of polishing surface to the surrounding part, are composed of the second kind of grooves  22  contacting each other at the central part and the second kind of grooves  22  does not contact any other second kind of grooves  22  at the central part, and do not intersect each other. 
     Although the main objective of the aforementioned patents is to effectively eliminate scratches caused by impurities produced in the interior when the polishing step is performed, yet when the scraps produced after polishing or the polishing particles in the slurry are larger than the groove, they cannot instantly flow out via the groove of polishing pad. And thus the residual polishing particles or deposits will form larger particles and easily cause scratching and damaging of surface of the polished work piece. 
     SUMMARY OF THE INVENTION 
     In order to solve the problems as described above, one objective of the present invention is to provide a polishing pad with two kinds of groove patterns. Therefore when the polishing step is performed, smaller scraps or smaller polishing particles or turbid slurry can flow out of the polishing pad via the second groove, and larger scraps or particles can flow out of the polishing pad via the first groove, and thus the polishing particles or deposits will not easily remain on the polishing pad or further cause scratching and damaging of surface of the polished work piece. 
     Another objective of the present invention is to provide a polishing pad, the design of groove of polishing surface of which facilitates the increase of friction force between the polishing pad and the work piece. 
     Still another objective of the present invention is to provide a polishing pad, the design of groove of polishing surface of which makes it easy for the slurry to be flung out with the centrifugal force function during the polishing step to prevent polishing particles from remaining or depositing. 
     Yet another objective of the present invention is to provide a polishing pad, the groove of which ensures that the slurry is evenly distributed on the polishing surface. 
     According to objectives described above, the present invention provides a polishing pad that includes a polishing surface, on the polishing surface being formed with at least a first groove and at least a second groove, wherein the characteristic of the polishing pad is in that: the first groove and the second groove are connected to each other, and the width of the first groove is larger than that of the second groove, and the depth of the first groove is larger than that of the second groove. Therefore when the polishing step is performed using the polishing pad, smaller scraps or smaller polishing particles or turbid slurry can flow out of the polishing pad via the second groove, and larger scraps or particles can flow out of the polishing pad via the first groove. Thus the polishing particles or deposits will not easily remain on the polishing pad or further cause scratching and damaging of the surface of polished work piece. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention as well as a preferred mode of use, further objectives and advantages thereof will best be understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1A  is a front view of a polishing pad (prior art); 
         FIG. 1B  is a sectional view of a polishing pad taken along sectional line a-a′ (prior art); 
         FIG. 2  is a front view of a polishing pad (prior art); 
         FIG. 3A  is a front view of a polishing pad; 
         FIG. 3B  is a sectional view of a polishing pad taken along sectional line b-b′; 
         FIG. 4  is a front view of a polishing pad; and 
         FIG. 5  is a front view of a polishing pad. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention discloses a polishing pad, and more particularly, a polishing pad with two kinds of groove patterns. In the present invention, some details for manufacturing or processing polishing pad are achieved by applying conventional art, and therefore are not completely depicted in below description. And the drawings referred to in the following are not made according to the actual related sizes, the function of which is only to express and illustrate characteristics of the present invention. 
     First, referring to  FIG. 3A  and  FIG. 3B , which are views of a preferred embodiment according to the present invention. Shown in  FIG. 3A  is a polishing pad  30  that includes a polishing surface,  30 A (as shown in  FIG. 3B ), and a plurality of first grooves  31  and a plurality of second grooves  32  are formed on the polishing surface  30 A to facilitate the increase of friction force between the polishing pad  30  and the work piece, wherein the characteristic of polishing pad  30  is in that: the first grooves  31  and the second grooves  32  are connected to each other, and the width of the first groove  31  is larger than that of the second groove  32 , the depth of the first groove  31  is larger than that of the second groove  32 , and the density of the first groove  31  distributed over the polishing surface  30 A is smaller than that of the second groove  32 , as shown in the sectional view of  FIG. 3B . Besides, the first groove  31  and the second groove  32  are uniformly distributed over the polishing surface  30 A respectively, as shown in  FIG. 3A . Therefore when the polishing step is performed using polishing pad, smaller scraps produced after polishing or smaller polishing particles in the slurry or turbid slurry can flow out of the polishing pad via the second groove, and larger scraps or particles can flow out of the polishing pad via the first groove, and thus the polishing particles or deposits will not easily remain on the polishing pad or further cause scratching and damaging of surface of the polished work piece. 
     Moreover, one end of first groove  31  and one end of second groove  32  are connected to the periphery of polishing pad  30  respectively, which thus makes it easy for the slurry to be flung out with the centrifugal force function during the polishing step; each of first grooves  31  has a uniform width and a uniform depth, each of second grooves  32  has a uniform width and a uniform depth; the depth of second groove  32  is 0.1 mm˜1 mm, with 0.4 mm˜0.7 mm being preferred embodiment, and the depth of first groove  31  is 0.2 mm˜1.5 mm, with 0.5 mm˜1.2 mm being preferred embodiment, therefore the depth of first groove  31  is larger than that of the second groove  32 ; the polishing pad  30  of the present invention further includes a connecting surface  30 B (as shown in  FIG. 3B ) for being connected to a polishing surface of another polishing pad to form a multi-layer polishing pad laid up by a plurality of layers of polishing pads. 
     Then, referring to  FIG. 3A , which is a view of a preferred embodiment of first groove of polishing pad according to the present invention. As shown in  FIG. 3A , the first groove  31  is disposed on the polishing pad  30  with the center of circle of polishing pad  30  as center in curved radiation toward the periphery of polishing pad  30 , the first groove  31  and the second groove  32  are uniformly distributed over the polishing surface  30  respectively, and is thus able to make it easy for the slurry to be flung out with the centrifugal force function during the polishing step to prevent the polishing particles from remaining or depositing; the second groove  32  is disposed on the polishing pad  30  in grid pattern to ensure that the slurry can be evenly distributed on the polishing surface for forming a polishing pad  30  with two kinds of groove patterns. 
     Referring to  FIG. 4 , which is a view of another preferred embodiment of first groove of polishing pad according to the present invention. As shown in  FIG. 4 , the first groove  41  is disposed on the polishing pad  40  with the center of circle of polishing pad  40  as center in direct line radiation toward the periphery of polishing pad  40 , the first groove  41  and the second groove  42  are uniformly distributed over the polishing surface  40  respectively, and is thus able to make it easy for the slurry to be flung out with the centrifugal force function during the polishing step to prevent the polishing particles from remaining or depositing; the second groove  42  is disposed on the polishing pad  40  in grid pattern to ensure that the slurry can be evenly distributed on the polishing surface for forming a polishing pad  40  with two kinds of groove patterns. 
     Referring to  FIG. 5 , which is a view of still another preferred embodiment of first groove of polishing pad according to the present invention. As shown in  FIG. 5 , the first groove  51  is disposed on the polishing pad  50  in grid pattern and the second groove  52  is also disposed on the polishing pad  50  in grid pattern, the first groove  51  and the second groove  52  are uniformly distributed over the polishing surface  50  respectively, and is thus able to ensure that the slurry can be evenly distributed on the polishing surface for forming a polishing pad  50  with two kinds of groove patterns. 
     What are described above are only preferred embodiments of the present invention and are not for limiting the scope of the present invention; and the above description can be understood and put into practice by those who are skilled in the art. Therefore any equivalent modifications and arrangements made without departing from the spirit disclosed by the present invention should be encompassed by the appended claims accorded with the broadest interpretation.