Abstract:
A chemical mechanical polishing (CMP) apparatus includes a plate that holds a substrate, a pad assembly unit comprising a pad support device, a positioning device, and a rotation device operatively connected to the pad assembly unit. The pad support device comprises a plurality of support plates to which pad pieces of a polishing pad can be attached. The positioning device can move at least one of the plurality of support plates in a direction along a surface of the semiconductor substrate to be polished. Further, the CMP apparatus can control the polishing amount along any portion of a surface of a wafer to be polished.

Description:
TECHNICAL FILED OF THE INVENTION  
         [0001]    The present invention relates, generally, to an apparatus for fabricating a semiconductor device and, more particularly, to a chemical mechanical polishing apparatus for polishing a surface of a semiconductor wafer.  
         BACKGROUND  
         [0002]    A semiconductor device fabricating process includes a deposition process for forming a thin film on a wafer and an etch process for forming a fine circuit pattern on the thin film. These processes are repeatedly carried out until a desired circuit pattern is formed on the wafer. Following formation of the circuit pattern, a large number of windings are formed at the surface of the wafer. With the recent trend toward finer semiconductor devices, the structure of semiconductor devices is multi-layered and the number of windings formed at the wafer surface and a step difference therebetween are increasing. If the wafer surface is not planarized, problems such as defocus occur during a photolithographic process. Thus, the wafer surface must periodically be polished so as to be planarized.  
           [0003]    A variety of surface planarizing techniques have been developed to planarize a wafer surface. Particularly, a chemical mechanical polishing (CMP) apparatus is widely used due to the superior planarity that can be obtained for a narrow area as well as a wide area.  
           [0004]    The CMP apparatus chemically mechanically polishes a wafer surface coated with tungsten or oxide and can achieve a very fine polishing. Mechanical polishing is performed by rotating a wafer that is pressed against a polishing pad, so there is a frictional force between the polishing pad and the wafer surface to polish the wafer surface. Chemical polishing is performed by polishing a wafer surface by feeding slurry, which is a chemical abrasive agent, between a polishing pad and a wafer.  
           [0005]    Referring to FIG. 1, a conventional chemical mechanical polishing (CMP) apparatus has a platen  120  to which a polishing pad  140  is attached, and a polishing head  160  is disposed over the platen  120 . A wafer is mounted on the polishing head  160  such that a polishing surface is disposed against a polishing pad. The polishing head  160  applies a controllable pressure to a rear surface of a wafer to polish the wafer.  
           [0006]    According to the above-described CMP apparatus, an entire surface of the wafer can regularly be polished while the amount of polishing a partial surface of the wafer cannot be controlled. Therefore, in a case where a wafer surface is winded because the deposition thickness on each part of the wafer is different, the windings are left even after the polishing process. That is, the wafer is not uniformly planarized.  
           [0007]    Generally, a diameter of the polishing pad  140  is at least two times larger than that of a wafer, and the wafer rotates on the axis of the polishing pad  140 . Thus, as the wafer diameter increases from 200 mm to 300 mm, the diameter of the polishing pad  140  becomes larger, thereby increasing manufacturing costs because a larger size polishing pad is required.  
           [0008]    Therefore, a need exists for a chemical mechanical polishing apparatus that uniformly planarizes a semiconductor wafer having a deposition of varying thickness on each portion of a wafer and that accommodates larger size semiconductors wafers without increasing the size of the polishing pad required to planarized a surface of a semiconductor wafer.  
         SUMMARY OF THE INVENTION  
         [0009]    Exemplary embodiments of the invention generally include a chemical mechanical polishing (CMP) apparatus which can readily regulate the amount of polishing for each part of a wafer and which does not require the diameter of a polishing pad to be increased as a diameter of a semiconductor wafer increases.  
           [0010]    According to an exemplary embodiment of the present invention, a chemical mechanical polishing (CMP) apparatus comprises a plate that holds a substrate, a pad assembly unit comprising a pad support device and a positioning device, wherein the pad support device comprises a plurality of support plates to which pad pieces of a polishing pad can be attached, and wherein the positioning device can move at least one of the plurality of support plates in a direction along a surface of the substrate to be polished, and a rotation device operatively connected to the pad assembly unit.  
           [0011]    According to another exemplary embodiment of the present invention, the CMP apparatus includes a polishing pad including pad pieces. The polishing pad has a circular shape, a triangular shape, a quadrangular shape, or an elliptical shape. The positioning device moves at least one of the plurality of support plates to a position between a center region and an edge region of a substrate. The positioning device includes a motor, a screw that rotates by operation of the motor, and a rod which is connected to one of the plurality of support plates and which moves by rotation of the screw. In another embodiment, a CMP apparatus further comprises a controller to control a rotation speed of the motor.  
           [0012]    According to still another exemplary embodiment of the present invention, the plurality of support plates includes a fixed support plate and a plurality of movable support plates disposed around the fixed support plate. The positioning device includes a motor, a screw that rotates by operation of the motor, and a rod which is connected to one of the movable support plates and which moves by rotation of the screw. According to another embodiment, the CMP apparatus comprises a controller to control a rotation speed of the motor.  
           [0013]    According to another embodiment, a CMP apparatus comprises a polishing pad including pad pieces. Preferably, the polishing pad including the pad pieces has a circular shape, a triangular shape, or an elliptical shape.  
           [0014]    According to yet another exemplary embodiment of the present invention, a chemical mechanical polishing (CMP) apparatus comprises a plate that holds a substrate, a pad assembly unit comprising a pad support device and a positioning device. The pad support device comprises a plurality of support plates to which pad pieces of a polishing pad can be attached. The positioning device comprises a housing, a plurality of motors attached to the housing, a plurality of screws rotatably attached to the housing, wherein each screw is coupled to a corresponding motor, and a plurality of connecting rods each having a screw groove, wherein each connecting rod is coupled to a corresponding support plate and to a corresponding screw through the screw groove. The CMP apparatus further comprises a rotation device operatively connected to the pad assembly unit.  
           [0015]    According to another embodiment, each motor of the positioning device rotates a corresponding screw to move a corresponding support plate back and forth along an axial direction of the screw.  
           [0016]    According to another embodiment, the rotational device operatively coupled to the housing rotates the housing and the plurality of support plates about the substrate to be polished.  
           [0017]    According to another embodiment, the CMP apparatus further comprises a controller to control a rotation speed of the motors.  
           [0018]    According to another embodiment, the plurality of support plates together forms a circular shape, a quadrangular shape, a triangular shape, or an elliptical shape.  
           [0019]    According to another embodiment, the plurality of support plates includes a fixed support plate and a plurality of movable support plates disposed around the fixed support plate. Preferably, the fixed support plate is a circular shape, a triangular shape, or an elliptical shape, and the movable support plates disposed around the fixed support plate form a circular shape, a triangular shape, or an elliptical shape.  
           [0020]    According to another embodiment, the CMP apparatus further comprises a polishing pad comprising a plurality of pad pieces attached to the plurality of support plates. Preferably, the polishing pad has a circular shape, a triangular shape, a quadrangular shape, or an elliptical shape.  
           [0021]    According to still yet another exemplary embodiment of the present invention, a pad assembly unit for a chemical mechanical polishing (CMP) apparatus comprises a pad support device comprising a plurality of support plates to which pad pieces of a polishing pad can be attached, and a positioning device that can move at least one of the plurality of support plates in a direction along a surface of a substrate to be polished.  
           [0022]    These and other exemplary embodiments, features, aspects, and advantages of the present invention will be described and become apparent from the following detailed description of the exemplary embodiments when read in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    [0023]FIG. 1 is a perspective view of a typical chemical mechanical polishing (CMP) apparatus.  
         [0024]    [0024]FIG. 2 is a perspective view of a CMP apparatus according to an exemplary embodiment of the present invention.  
         [0025]    [0025]FIG. 3A and FIG. 3B is a cross-sectional view and a bottom view of a pad assembly shown in FIG. 2.  
         [0026]    [0026]FIG. 4A through FIG. 4D illustrate various phenomena of a polishing pad shown in FIG. 3B.  
         [0027]    [0027]FIG. 5A through FIG. 5C illustrate polishing pads having a various number of pad pieces.  
         [0028]    [0028]FIG. 6A and FIG. 6B are a cross-sectional view and a bottom view showing that the respective pads pieces concentrate at the center of a wafer in accordance with the exemplary embodiment of FIGS. 3A and 3B.  
         [0029]    [0029]FIG. 7A and FIG. 7B are a cross-sectional view and a bottom view showing the pad pieces move a predetermined distance along a radius direction of a wafer in accordance with the exemplary embodiment of FIGS. 3A and 3B.  
         [0030]    [0030]FIG. 8A and FIG. 8B are a cross-sectional view and a bottom view showing that the pad pieces have moved to the edge of a wafer edge in accordance with the exemplary embodiment of FIGS. 3A and 3B.  
         [0031]    [0031]FIG. 9A and FIG. 9B are a cross-sectional view and a bottom view of a pad assembly according to another exemplary embodiment of the present invention.  
         [0032]    [0032]FIG. 10A through FIG. 10C illustrate various shapes of a polishing pad shown in FIG. 9B.  
         [0033]    [0033]FIG. 11A through FIG. 11C illustrate polishing pads having the various number of pad pieces.  
         [0034]    [0034]FIG. 12A and FIG. 12B are a cross-sectional view and a bottom view showing that the respective pad pieces concentrate at the center of a wafer in accordance with the exemplary embodiment of FIGS. 9A and 9B.  
         [0035]    [0035]FIG. 13A and FIG. 13B are a cross-sectional view and a bottom view showing that the pad pieces move a predetermined distance along a radius direction of a wafer in accordance with the exemplary embodiment of FIGS. 9A and 9B.  
         [0036]    [0036]FIG. 14A and FIG. 14B are a cross-sectional view and a bottom view showing that the pad pieces move to the edge of a wafer edge in accordance with the exemplary embodiment of FIGS. 9A and 9B. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0037]    A chemical mechanical polishing (hereinafter referred to as “CMP”) apparatus according to an exemplary embodiment of the present invention will now be described with reference to FIG. 2. The CMP apparatus includes a rotation plate  220 , a pad assembly (or pad assembly unit)  300  and a vertical move part  240 .  
         [0038]    The plate  220  is a circular plate where a wafer W is fixed during a CMP process. A rotation axis (not shown) for supporting the plate  220  and a rotation motor (not shown) for rotating a plate and a rotation axis at a regular speed may be installed below the plate  220 . A wafer may be fixed on the plate  220  by means of a chemical clamp or by vacuum absorption.  
         [0039]    The pad assembly  300  for polishing a top surface of the wafer W is installed over the plate  220 . The pad assembly  300  can be moved up and down by the vertical move part  240 . A slurry-feeding arm (not shown) for feeding slurry onto the surface of the wafer W may be disposed at an upper lateral side of the plate  220 .  
         [0040]    [0040]FIG. 3A is a cross-sectional view of the pad assembly  300  according to an exemplary embodiment of the present invention, and FIG. 3B is a bottom view thereof. Referring to FIG. 3A and FIG. 3B, the pad assembly  300  has a polishing pad  320 , a support part (or pad support device)  340 , a horizontal move part (or positioning device)  520 , a rotation part (or rotational device)  380 , and a controller  400 .  
         [0041]    The polishing pad  320  is a flat pad having a predetermined thickness and is in direct contact with a wafer W to mechanically polish the wafer W. The polishing pad  320  is supported by the support part  340  and rotates with the support part  340  during a process. In this invention, the polishing pad  320  may have various shapes. For example, the polishing pad  320  may have a circular pad shape, as shown in FIG. 4A. Alternatively, the polishing pad  320  may have an elliptic pad shape, as shown in FIG. 4B. Alternatively, the polishing pad  320  may have a polygonal pad shape (e.g., triangle or quadrangle), as shown in FIGS. 4C and 4D. The polishing pad  320  has a smaller cross-sectional area than a wafer. For example, in a case where the polishing pad  320  has a circular shape, the polishing pad  320  may have a ½ to ⅓ smaller diameter than the wafer W.  
         [0042]    In this embodiment, the polishing pad  320  comprises a plurality of pad pieces  322 . In a case where the polishing pad has a circular pad shape, each of the pad pieces  322  may have the shape of a fan whose central angle is 45°. Unlike this, as shown in FIG. 5A, FIG. 5B, and FIG.  5 C, the polishing pad  320  may comprise two, three or four pad pieces  322 . In addition, the polishing pad may comprise more than four pad pieces.  
         [0043]    The polishing pad  320  is attached to the support part  340 , wherein the support part  340  has the same shape as the polishing pad  320 . The support part  340  has a plurality of support plates to which the respective pad pieces  322  are attached. Each of the support plates  342  may have the same shape and size as the pad piece  322 .  
         [0044]    A horizontal move part  520 , or positioning device, is disposed on the support part  340  to move the respective pieces  322  of the polishing pad  320  from the center of a wafer W to the edge thereof or from the edge of the wafer W to the center thereof. The horizontal move part  520  has a housing  310 , a fixed projection  330 , screws  360 , connecting rods  350 , and motors  370 . The housing  310  has the shape of a cylinder whose bottom is open, and constitutes an outward form of the horizontal move part  520 . The fixed projection  330  is disposed at the center of an upper portion inside the housing  310 . One end of the respective screws  360 , which are uniformly disposed, is inserted into the fixed projection  330 . The number of the screws  360  is equal to that of the pad pieces  322 . The motor  370  is connected to the other end of the respective screws  360 . The screws  360  have a length that allows the pad pieces  322  to be moved from a center portion of a wafer to an edge portion of a wafer. One end of the respective connecting rods  350  is fixed to an upper portion of the support plate  342  disposed at a corresponding position. A screw groove, into which the screw  360  is inserted, is formed at the other end of the respective connecting rods  350 . That is, when the motor  370  rotates in one direction, the screw  360  connected thereto rotates to straightly move the support plate  342 , to which the pad pieces  322  are attached, from the center of the wafer to the edge thereof or from the edge of the wafer to the center thereof.  
         [0045]    A rotation part  380 , or rotational device, for rotating the horizontal move part  520  and the polishing pad  320  is connected to a top portion of the horizontal move part  520 . The rotation part  380  has a driving axis  384  and a motor  382 . The driving axis  384  is fixed to a center of the top portion of the horizontal move part  520 , and the motor  382  for rotating the driving axis  384  is connected to a top portion of the driving axis. By the rotation part  380 , the polishing pad  320  rotates on the driving axis  384  in the same direction as a wafer W or in the reverse direction to the wafer W.  
         [0046]    [0046]FIG. 6A and FIG. 6B show that the respective pad pieces  322  concentrate at the center of a wafer W during a polishing process in accordance with the exemplary embodiment of FIGS. 3A and 3B, respectively. FIG. 7A and FIG. 7B show that the pad pieces  322  are dispersed in the middle of the wafer W. FIG. 8A and FIG. 8B show that the pad pieces  322  are dispersed at the edge of the wafer W.  
         [0047]    As shown in FIG. 6A and FIG. 6B, when a polishing process starts, the pad pieces  322  concentrate at the center of the wafer W to make the polishing pad  320  have a circular shape. When the polishing process is carried out, a horizontal move part  520  rotates together with the polishing pad  320  by a rotation part  380 . As a motor  370  rotates in one direction, the respective pad pieces move to the middle of the wafer W to be dispersed, as shown in FIG. 7A and FIG. 7B. If the motor  370  continuously rotates in one direction, the pad pieces moves to the edge of the wafer W, as shown in FIG. 8A and FIG. 8B. If the motor  370  rotates in the other direction, the pad pieces  322  move from the edge of the wafer W to the center thereof through the middle thereof. During the polishing process, the plate  220  to which the wafer W is fixed may be shaken even by a short stroke.  
         [0048]    During the polishing process, the wafer W may be polished while the respective pad pieces  322  successively move from the center of the wafer W to the edge thereof or sojourns at a specific position on the wafer W for a predetermined time. For this, a controller  400  for controlling a rotation speed of the motor  370  is provided. For example, when a deposition has a greater thickness at the edge of the wafer than at the center of the wafer, the time the pad pieces  322  sojourn at the edge of the wafer W may be longer than the time the pad pieces  322  sojourn at the center of the wafer W or in the middle thereof.  
         [0049]    [0049]FIG. 9A is a cross-sectional view of a pad assembly  300  according to another exemplary embodiment of the present invention, and FIG. 9B is a bottom view of the pad assembly  300  shown in FIG. 9A. Referring to FIG. 9A and FIG. 9B, the pad assembly  300  has a polishing pad  420 , a support part  440 , a horizontal move part  540 , and a rotation part  480 .  
         [0050]    Similar to the exemplary embodiment of FIGS. 3A and 3B, the polishing pad  420  comprises a plurality of pad pieces  422  and  424 . But the pad piece  424  is a fixed pad piece disposed at the center of a wafer, and the pad pieces  422  are move pad pieces disposed at the edge thereof.  
         [0051]    The polishing pad  420  may have various shapes. For example, the polishing pad  420  may have a circular pad shape, as shown in FIG. 10A. Alternatively, the polishing pad  420  may have an elliptical pad shape, as shown in FIG. 10B. Alternatively, the polishing pad  420  may have a triangle pad shape, as shown in FIG. 10C, or a polygonal pad shape (e.g., quadrangular pad shape). In a case where the polishing pad has a circular pad shape, the fixed pad piece  424  has a circular shape and the move pad pieces  422  may be divided into eight parts so as to have a uniform shape. In addition, as shown in FIG. 11A, FIG. 11B, and FIG. 11C, the move pad pieces  422  may be divided into two, three or four parts. Further, the pad pieces  422  may be divided into more than four pieces.  
         [0052]    The construction and shape of the horizontal move part  540 , or positioning device, according to the exemplary embodiment of FIGS. 9A and  9 B are similar to those of the horizontal move part  520  according to the exemplary embodiment of FIGS. 3A and 3B. However, the support part  440  has a fixed support plate  444  to which the fixed pad piece  424  is attached, and a plurality of move support plate  442  to which the move pad pieces  422  are attached. The shape and size of the fixed support plate  444  and the move support plates  442  may be identical to those of the fixed pad piece  424  or the move pad pieces  422 . The fixed support plate  444  is directly connected to a fixed projection  430  by a supporting rod  452  to be disposed at the center of a wafer W during a polishing process and does not move toward the edge of the wafer W. Each of the move support plates  442  is coupled to a connecting rod  450  into which a screw  460  is inserted, and is straightly moved by the rotation of the motor  470  during the polishing process.  
         [0053]    [0053]FIG. 12A and FIG. 12B show that the respective pad pieces  422  and  424  concentrate at the center of a wafer W in accordance with the exemplary embodiment of FIGS. 9A and 9B. FIG. 13A and FIG. 13B show that the move pad pieces  422  are dispersed in the middle of the wafer W. FIG. 14A and FIG. 14B show that the move pad pieces  422  are dispersed at the edge of the wafer W.  
         [0054]    As shown in FIG. 12A and FIG. 12B, when a polishing process starts, the pad pieces  422  and  424  concentrate at the center of the wafer W to make the polishing pad  420  have a circular shape. When a polishing process is carried out, the horizontal move part  540  rotates, together with polishing pad  420 , on a driving axis  484  by a motor  482 . As the motor  470  rotates in one direction, the pad piece  424  stays at the center of the wafer W and the respective move pad pieces  422  move toward the middle of the wafer W. If the motor  470  continuously rotates in one direction, the move pad pieces  422  continuously move toward the edge of the wafer W, as shown in FIG. 14A and FIG. 14B.  
         [0055]    In the exemplary embodiment of FIGS. 3A and 3B, since fan-shaped pad pieces  322  are used, the insides of the pad pieces  322  are pointed. Thus, a wafer W may be unpolished at portions contacting the pointed insides. But in the exemplary embodiment of FIGS. 9A and 9B, in a case where a circular or elliptical polishing pad  420  is used, the inside of a move pad piece  422  has a constant width. Thus, a wafer W is normally polished at a portion of the wafer contacting the inside of the move pad piece  422  having the constant width.  
         [0056]    According to exemplary embodiments of the present invention as described above, a chemical mechanical polishing apparatus comprises a plurality of pad pieces, wherein each pad pieces can be moved from the center of a wafer to the outer edge of the wafer, and the sojourning time and position of the pad pieces can be controlled, thereby uniformly planarizing a semiconductor wafer. Thus, it is possible to obtain a uniform planarized surface of a semiconductor wafer having a deposition of varying thickness on the surface wafer