Abstract:
The present invention includes a polishing pad or belt secured to a mechanism that allows the pad or belt to move in a reciprocating manner, i.e. in both forward and reverse directions, at high speeds. The constant bidirectional movement of the polishing pad or belt as it polishes the wafer provides superior planarity and uniformity across the wafer surface. When a fresh portion of the pad is required, the pad is moved through a drive system containing rollers, such that the rollers only touch a back side of the pad, thereby minimizing sources of friction other than the wafer that is being polished from the polishing side of the pad, and maximizing the lifetime of the polishing pad.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]    This application is a continuation in part of application Ser. No. 09/684,059, filed Oct. 6, 2000, which is a continuation in part of application Ser. No. 09/576,064, filed May 22, 2000, now U.S. Pat. No. 6,207,572 issued Feb. 27, 2001, which is a continuation of application Ser. No. 09/201,928, filed Dec. 1, 1998, now U.S. Pat. No. 6,103,628 issued Aug. 15, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to the field of chemical mechanical polishing. More particularly, the present invention relates to methods and apparatus for polishing a semiconductor wafer to a high degree of planarity and uniformity. This is achieved when the semiconductor wafer is polished with pads at high bidirectional linear or reciprocating speeds. The present invention is further directed to a wafer housing for loading and unloading wafers.  
         BACKGROUND OF THE INVENTION  
         [0003]    Chemical mechanical polishing (CMP) of materials for VLSI and ULSI applications has important and broad application in the semiconductor industry. CMP is a semiconductor wafer flattening and polishing process that combines chemical removal of layers such as insulators, metals, and photoresists with mechanical polishing or buffering of a wafer layer surface. CMP is generally used to flatten surfaces during the wafer fabrication process, and is a process that provides global planarization of the wafer surface. For example, during the wafer fabrication process, CMP is often used to flatten/polish the profiles that build up in multilevel metal interconnection schemes. Achieving the desired flatness of the wafer surface must take place without contaminating the desired surface. Also, the CMP process must avoid polishing away portions of the functioning circuit parts.  
           [0004]    Conventional systems for the chemical mechanical polishing of semiconductor wafers will now be described. One conventional CMP process requires positioning a wafer on a holder rotating about a first axis and lowered onto a polishing pad rotating in the opposite direction about a second axis. The wafer holder presses the wafer against the polishing pad during the planarization process. A polishing agent or slurry is typically applied to the polishing pad to polish the wafer. In another conventional CMP process, a wafer holder positions and presses a wafer against a belt-shaped polishing pad while the pad is moved continuously in the same linear direction relative to the wafer. The so-called belt-shaped polishing pad is movable in one continuous path during this polishing process. These conventional polishing processes may further include a conditioning station positioned in the path of the polishing pad for conditioning the pad during polishing. Factors that need to be controlled to achieve the desired flatness and planarity include polishing time, pressure between the wafer and pad, speed of rotation, slurry particle size, slurry feed rate, the chemistry of the slurry, and pad material.  
           [0005]    Although the CMP processes described above are widely used and accepted in the semiconductor industry, problems remain. For instance, there remains a problem of predicting and controlling the rate and uniformity at which the process will remove materials from the substrate. As a result, CMP is a labor intensive and expensive process because the thickness and uniformity of the layers on the substrate surface must be constantly monitored to prevent overpolishing or inconsistent polishing of the wafer surface.  
           [0006]    Accordingly, an inexpensive and more consistent method and apparatus for polishing a semiconductor wafer are needed.  
         SUMMARY OF THE INVENTION  
         [0007]    It is an object of the present invention to provide methods and apparatus that polish a semiconductor wafer with uniform planarity.  
           [0008]    It is another object of the present invention to provide methods and apparatus that polish a semiconductor wafer with a pad having high bidirectional linear or reciprocating speeds.  
           [0009]    It is still another object of the present invention to provide a polishing method and system that provides a “fresh” polishing pad to the wafer polishing area, thereby improving polishing efficiency and yield.  
           [0010]    It is still a further object of the present invention to provide a drive system for providing the fresh polishing pad from a roll of a polishing pad such that the lifetime of the polishing pad is maximized.  
           [0011]    These and other objects of the present invention, among others, either singly or in combination, are obtained by providing methods and apparatus that polish a wafer with a pad having high bi-directional linear speeds. The present invention includes a polishing pad or belt secured to a mechanism that allows the pad or belt to move in a reciprocating manner, i.e. in both forward and reverse directions, at high speeds. The constant bidirectional movement of the polishing pad or belt as it polishes the wafer provides superior planarity and uniformity across the wafer surface. When a fresh portion of the pad is required, the pad is moved through a drive system containing rollers, such that the rollers only touch a back portion of the pad, thereby eliminating sources of friction other than the wafer that is being polished, and maximizing the lifetime of the polishing pad. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    These and other objects and advantages of the present invention will become apparent and more readily appreciated from the following detailed description of the presently preferred exemplary embodiment of the invention taken in conjunction with the accompanying drawings, of which:  
         [0013]    [0013]FIG. 1 illustrates a perspective view of a polishing method and apparatus in accordance with the first preferred embodiment of the present invention;  
         [0014]    [0014]FIG. 2 illustrates a side view of a polishing method and apparatus in accordance with the first preferred embodiment of the present invention;  
         [0015]    [0015]FIG. 3 illustrates a front view of a method and apparatus for attaching a polishing pad to timing belts in accordance with the first preferred embodiment of the present invention;  
         [0016]    [0016]FIG. 4 illustrates side views of a polishing pad moving around the timing belt rollers in accordance with the first preferred embodiment of the present invention;  
         [0017]    [0017]FIG. 5 illustrates a side view of a polishing apparatus and driving mechanism in accordance with the second preferred embodiment of the present invention;  
         [0018]    [0018]FIG. 6 illustrates a cross sectional view of the polishing apparatus and driving mechanism of FIG. 5 in accordance with the second preferred embodiment of the present invention;  
         [0019]    [0019]FIG. 7 illustrates a simplified illustration of a drive mechanism for providing a fresh portion of the polishing pad according to the present invention; and  
         [0020]    [0020]FIGS. 8A and 8B illustrate side and cross-sectional views of a polishing apparatus that includes a drive mechanism for providing a fresh portion of the polishing pad according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    The preferred embodiments of the present invention will now be described with reference to FIGS.  1 - 8 , wherein like components are designated by like reference numerals throughout the various figures. The present invention is directed to CMP methods and apparatus that can operate at high bidirectional linear pad or reciprocating speeds and a reduced foot-print. The high bidirectional linear pad speeds optimize planarity efficiency while the reduced foot-print reduces the cost of the polishing station. Further, because the polishing pad is adapted to travel in bi-directional linear directions, this reduces the pad glazing effect, which is a common problem in conventional CMP polishers. Because the pad travels in bi-directional linear directions, the pad (or pad attached to a carrier) is substantially self-conditioning.  
         [0022]    [0022]FIG. 1 illustrates a perspective view and FIG. 2 illustrates a side view of an apparatus of a first preferred embodiment of the present invention. The wafer polishing station  2  includes a bidirectional linear, or reverse linear, polisher  3  and a wafer housing  4 . The wafer housing  4 , which can rotate about its center axis and/or move side to side or vertically, securely positions a wafer  18  or workpiece so that a surface  17  may be polished. In accordance with the present invention, novel methods and apparatus of loading and unloading the wafer  18  onto the wafer housing  4  is described more fully later herein.  
         [0023]    The reverse linear polisher  3  includes a polishing pad  6  for polishing the wafer surface  17 , a mechanism  8  for driving the polishing pad  6  in a bi-directional linear or reciprocating (forward and reverse) motion, and a support plate  10  for supporting the pad  6  as the pad  6  polishes the wafer surface  17 . A polishing agent or slurry containing a chemical that oxidizes and mechanically removes a wafer layer is flowed between the wafer  18  and the polishing pad  6 . The polishing agent or slurry such as colloidal silica or fumed silica is generally used. The polishing agent or slurry generally grows a thin layer of silicon dioxide or oxide on the wafer surface  17 , and the buffering action of the polishing pad  6  mechanically removes the oxide. As a result, high profiles on the wafer surface  17  are removed until an extremely flat surface is achieved. It should also be noted that the size of the particles from the polishing agent or slurry used to polish the wafer surface  17  is preferably at least two or three times larger than the feature size of the wafer surface  17 . For example, if the feature size of the wafer surface  17  is 1 micron, then the size of the particles should be at least 2 or 3 microns.  
         [0024]    The underside of the polishing pad  6  is attached to a flexible but firm and flat material (not shown) for supporting the pad  6 . The polishing pad  6  is generally a stiff polyurethane material, although other suitable materials may be used that is capable of polishing wafer surface  17 . In addition, the polishing pad  6  may be non-abrasive or abrasive, depending on the desired polishing effect and chemical solution used.  
         [0025]    In accordance with the first preferred embodiment of the present invention, the driving or transmission mechanism  8  for driving the polishing pad  6  in a bi-directional linear motion will now be described. Although FIGS.  1 - 2  illustrate only one driving mechanism  8  from the front side of the reverse linear polisher  3 , it is understood that on the backside of the reverse linear polisher  3 , a similar driving mechanism  8  is also present. Driving mechanism  8  includes three timing belts, two vertically suspending timing belts  14 ,  15  and one horizontally suspending timing belt  16 . The timing belts  14 ,  15 , and  16  may be formed of any suitable material such as stainless steel or high strength polymers having sufficient strength to withstand the load applied to the belts by the wafer  18 . One end of the vertically suspending timing belts  14 ,  15  is secured to rollers  20  while the other end is secured to rollers  22 . Likewise, each end of the horizontally suspending timing belt  16  is secured to rollers  20 . As illustrated in FIG. 1, it is noted that the horizontally suspending timing belt  16  is placed in a z-plane slightly outside the z-plane of the vertically suspending timing belts  14 ,  15 .  
         [0026]    Rollers  20  link the two vertically suspending timing belts  14 ,  15  with the horizontally suspending timing belt  16  so that each belts rate of rotation depends on the rate of rotation of the other belts. The rollers  20  and  22  retain the timing belts  14 ,  15 , and  16  under proper tension so that the polishing pad  6  is sufficiently rigid to uniformly polish the wafer surface  17 . The tension of the timing belts may be increased or decreased as needed by adjusting the position of rollers  22  relative to roller  20 .  
         [0027]    Although one embodiment of the present invention describes a driving mechanism having three timing belts secured on four rollers, it is understood that any suitable number of rollers and/or timing belts, or a driving mechanism that does not rely on rollers/belts, i.e. a seesaw mechanism, such that it provides the bidirectional linear or reciprocating motion, are intended to be within the scope and spirit of the present invention.  
         [0028]    An important aspect of one embodiment of the present invention is that the polishing pad  6  and the corresponding support material is adapted to bend at an angle at corners  24 , which angle is preferably about 90°. Each end of the polishing pad  6  is attached to a point on the two vertically positioned timing belts  14 ,  15  by attachments  12 ,  13 . One end of the polishing pad  6  is secured to attachment  12 , and the other end is secured to attachment  13 . Attachments  12  and  13  are preferably a sleeve and rod, as more fully described later herein. Referring again to FIGS. 1 and 2, as one end of the polishing pad  6  travels vertically downward with the assistance of timing belt  14  and attachment  12 , the other end of the polishing pad  6  travels vertically upward with the assistance of timing belt  15  and attachment  13 . The mechanical alignment of the timing belts  14 ,  15 , and  16  with the rollers  20  and  22  allows such movement to occur.  
         [0029]    In order to drive the timing belts  14 ,  15 , and  16  to a desired speed, a conventional motor (not shown) is used to rotate rollers  20  and/or  22 . The motor is connected to rollers  20  or  22  or to any suitable element connected to rollers  20  and/or  22 , and it provides the necessary torque to rotate rollers  20  and  22  to a desired rate of rotation. The motor directly/indirectly causes rollers  20  and  22  to rotate so that the timing belts  14 ,  15 , and  16  are driven at a desired speed in both forward and reverse directions. For instance, when attachment  13  reaches roller  22  during its downward motion, it will reverse the direction of the polishing pad  6  as attachment  13  now travels upward. Soon thereafter, the same attachment  13  now reaches roller  20  and again changes direction in a downward direction. The reciprocating movement of attachment  13  allows the polishing pad  6  to move in both forward and reverse directions. Preferably, the speed at which the polishing pad  6  is moved is within the range of approximately 100 to 600 feet per minute for optimum planarization of the wafer surface  17 . However, it should be understood that the speed of the polishing pad  6  may vary depending on many factors (size of wafer, type of pad, chemical composition of slurry, etc.). Further, the pad  6  may be moved in both bidirectional linear directions at a predetermined speed, which preferably averages between 100 to 600 feet per minute.  
         [0030]    [0030]FIG. 3 illustrates a front view and FIG. 4 illustrates a side view of a method and apparatus for attaching the polishing pad  6  to the timing belts  14 ,  15  in accordance with the first preferred embodiment of the present invention. As described earlier herein, the underside of the polishing pad  6  is attached to the flexible but firm and flat material, which is non-stretchable. At each end of the material, and thus the ends of the polishing pad  6 , a rod  40  is attached. The rod  40  extends horizontally from the pad  6  as shown in FIG. 3. A sleeve  42 , i.e. a cylinder or a slit, is also attached to each of the vertically suspending timing belts  14 ,  15 , and a portion  44  of the sleeve  42  extends horizontally to join the rod  40 , as again illustrated in FIG. 3. When the rod  40  and the sleeve  42  are joined, this allows the polishing pad  6  to travel bidirectional with high linear speeds without the problem of having the polishing pad  6  being wrapped around the rollers  20 ,  22 . FIG. 4 further illustrates a side view of the polishing pad  6  as it rotates around the rollers  20 ,  22 .  
         [0031]    As described earlier, the polishing pad  6  bends at an angle, preferably about 90° at the two corners  24 , in accordance with one embodiment of the invention. This approach is beneficial in this embodiment for various reasons. Since the length of the polishing pad  6  on the horizontal plane needed to polish the wafer surface  17  needs to be only slightly longer than the wafer  18  diameter, the entire length of polishing pad should be only slightly longer than three times the wafer  18  diameter, in accordance with this embodiment. This allows the most efficient and economical use of the entire polishing pad  6 . During polishing, slurry or other agent may be applied to the portions of the polishing pad  6  that are not in contact with the wafer surface  17 . The slurry or other agent can be applied to the polishing pad preferably at locations near corners  24 . The configuration of the polishing pad  6  described above also decreases the size of a support plate  10  needed to support the pad  6 . Furthermore, though the bidirectional linear movement provides for a substantially self conditioning pad, a conditioning member can also be disposed on or about this same location.  
         [0032]    The novel approach described above has many other advantages and benefits. For example, the CMP device of the present invention takes up less space than most traditional CMP devices because about two-thirds of the polishing pad  6  can be in a vertical position. The bi-directional linear movement of the CMP device further increases the pad usage efficiency because the reciprocating movement of the pad  6  provides a self-conditioning function, since the pad  6  is moving in different, preferably opposite, directions.  
         [0033]    In accordance with the present invention, only one wafer is generally polished during a single time. As described above, the polishing pad  6  moves bidirectional with high linear speeds so as to uniformly polish the wafer surface  17 . Because high pad speeds are needed to polish the wafer surface  17 , the momentum, and thus inertia created is very high. Thus, as the polishing pad  6  reverses direction, sufficient energy is needed to keep the pad moving at desired speeds. If the total area (length and width) of the polishing pad  6  is minimized, the energy needed to keep the pad moving at desired speeds is decreased accordingly. Thus, by limiting the length of the polishing area of the polishing pad  6 , a conventional motor can handle the necessary energy needed to keep the pad moving at desired speeds in both forward and reverse directions. The entire length of the active polishing area of the polishing pad  6  should preferably be slightly longer than two-diameter lengths of the wafer  18 , and preferably three-diameter lengths of the wafer  18 . The reason for this is so that the polishing pad  6  may be conditioned and slurry may be applied to both sides of the pad opposite where the wafer  18  is positioned, in close proximity to corners  24 . Also, although it is preferred that the polishing pad  6  width is wider than the wafer diameter, in other embodiments, the width of the polishing pad  6  may be smaller than the wafer diameter.  
         [0034]    Although the present invention is adapted to polish a single wafer at one time, one skilled in the art may modify the preferred embodiment of the invention in order to polish multiple wafers at one time. Slurry (not shown) can be applied to the surface of the polishing pad  6  in conventional manners and the pad  6  can further be conditioned in conventional manners.  
         [0035]    Referring again to FIGS.  1 - 2 , the support plate  10  for supporting the polishing pad  6  will now be described. The polishing pad  6  is held against the wafer surface  17  with the support of the support plate  10 , which may be coated with a magnetic film. The backside of the support material to which the polishing pad  6  is attached may also be coated with a magnetic film, thus causing the polishing pad  6  to levitate off the support plate  10  while it moves at a desired speed. It should be understood that other conventional methods can be used to levitate the polishing pad  6  off the support plate  10  while it polishes the wafer surface  17 , such as air, magnetic, lubricant, and/or other suitable liquids.  
         [0036]    [0036]FIGS. 5 and 6 illustrate side and cross sectional views (along line I-I), respectively, of a polishing apparatus and driving mechanism in accordance with the second preferred embodiment of the present invention. Reference will be made concurrently to FIGS. 5 and 6 for a more complete understanding of the second preferred embodiment of the present invention.  
         [0037]    The polishing apparatus  100  includes a driving mechanism having a bi-directional linear, or reverse linear, polishing belt  110  for polishing a wafer (not shown) that is supported by the wafer housing  4  (not shown), which is described in greater detail later herein. A processing area  116  of the apparatus  100  includes a section of the polishing belt  110  that is supported by a platen  123 , which platen  123  is capable of providing “gimbaling” action for leveling/suspending the section of the polishing belt  110  above it. In addition, an air or magnetic bearing may be positioned underneath the section of the polishing belt  110  in the processing area  116  to control the pressure between the polishing belt  110  and the wafer surface during the polishing process.  
         [0038]    Besides the processing area  116 , the polishing apparatus  100  includes in its top portion a supply spool  111 , a receiving spool  115 , and idle rollers  112   a ,  112   b ,  112   c ,  112   d . In addition, the apparatus  100  includes a pair of rocker arms  114   a ,  114   b , each having rocker bearings  117   a ,  117   b , respectively, connected thereto via a shaft  132 . Further connected to each end of the rocker arms  114   a ,  114   b  are a pair of rocker arm rollers  113   a ,  113   b , which are capable of moving about within the railings  118   a ,  118   b , respectively. The shaft  132  connecting the pair of rocker arms  114   a ,  114   b  is further connected to a drive crank  119  through an elbow  120  and a connecting rod  121 . As shown, the connecting rod  121  can be fixed to the drive crank  119  at position  122 . Additionally, a first motor  131  is connected to the drive crank  119  for rotating the same, which operation is described in greater detail below.  
         [0039]    During operation in accordance with the second preferred embodiment, the polishing belt  110  originates from the supply spool  111  to a first idle roller  112   a . Although not expressly illustrated, a conventional clutch mechanism is connected to the supply spool  111 , which is used to adjust the tension of the polishing belt  110  between the supply spool  111  and the receiving spool  115 . The polishing belt  110  is then routed around the first idle roller  112   a  and a first rocker arm roller  113   a  to a second idle roller  112   b . The polishing belt  110  is again routed around the second idle roller  112   b  to a third idle roller  112   c . Thereafter, the polishing belt  110  is routed around a second rocker arm roller  113   b  and a fourth idle roller  112   d  to the receiving spool  115 .  
         [0040]    A second conventional motor (not shown) is connected to the receiving spool  115  for rotating the same so that sections of the polishing belt  110  can be pulled from the supply spool  111  to the receiving spool  115 . For example, when the second motor is activated and the clutch resistance is properly adjusted, the second motor rotates the receiving spool  111  in a manner such that sections of the polishing belt  110  are received therein. In a similar manner, the tension of the polishing belt  110  between the supply spool  111  and receiving spool  115  can be adjusted by providing the appropriate motor torque and clutch resistance. This technique can be used to provide the proper contact pressure between the polishing belt  110  and the wafer surface in the processing area  116 .  
         [0041]    When a section of the polishing belt  110  is positioned in the processing area  116 , the first motor  131  can be activated to rotate the drive crank  119  in a circular manner. This in turn allows the connecting rod  121  to push the elbow  20  upwards, thereby moving the right section  140  of the rocker arm  114  upwards. This allows the first rocker arm roller  113   a  to move upwards (from the position as illustrated in FIG. 5) along the right railing  118   a . Simultaneously, this causes the second rocker arm roller  113   b  on the left section  142  of the rocker arm  114  to move downwards along the left railing  118   b . Thus, as the drive crank  119  is continuously rotated, the first and second rocker arm rollers  113   a ,  113   b  continue to move up and down along right and left railings  118   a ,  118   b , respectively, thereby causing the section of the polishing belt  110  in the processing area  116  to move in the bidirectional or reverse linear motion. Polishing chemicals (i.e., slurry) such as those described above are provided between the polishing belt  110  and the wafer surface.  
         [0042]    After the section of the polishing belt  110  is used to polish one or more wafers in the processing area  116 , a new section of the polishing belt  110  is fed to the processing area  116  in the manner described above. In this manner, after one section of the polishing belt  110  is worn out, damaged, etc., the new section can be used. Consequently, using the present invention, all or most sections of the polishing belt  110  in the supply spool  111  will be used. It is noted that the feeding of a new section of the polishing belt  119  to the processing area  116  can occur in between times that polishing of the wafers is occurring, or the polishing belt  110  can gradually be advanced, such that the new section of the polishing is a new portion, along with a portions that have been previously used, with that portion of the polishing belt that is within the polishing area and closest to the receiving spool  115  having been used the most, and that portion of the polishing belt that is within the polishing area and closest to the supply spool  111  having been used the least.  
         [0043]    Although the second preferred embodiment describes an apparatus and driving mechanism having four idle rollers, two rockers arm rollers, two rocker arms, etc., it is understood that any suitable number of idle rollers, rocker arm rollers, rocker arms, etc., can be used to provide the bidirectional linear or reciprocating motion and is intended to be within the spirit and scope of the present invention. In addition, other similar components/devices may be substituted for the ones described above.  
         [0044]    In addition, the layout or geometry of the polishing pad/belt with respect to the wafer as illustrated in the first and second embodiments can be changed from those illustrated herein to other positions. For example, one can position the polishing pad/belt above the wafer, position the polishing pad/belt vertically with respect to the wafer, etc.  
         [0045]    [0045]FIG. 7 provides a simplified illustration of a drive mechanism for providing a fresh portion of the polishing pad according to the present invention, which provides for a translation of rotational motion to linear up and down motion. As is apparent, rotation of an axle, for example illustrated as axle  731  associated with motor  732  will result in rotation of two drive mounts  738  and  740 . To each of these drive mounts is attached some motion translation mechanism  742  and  744 , respectively, which are 180 degrees out of phase as attached to the drive mounts  738  and  740 , respectively, and also which are attached to different end portions  710   a  and  710   b  of the polishing belt  710 , which polishing belt is preferably supported in position, and in particular an appropriate position within a polishing area (not shown), by a support mechanism, shown for example as rollers  712 , from a backside of the polishing belt. Rotation of the drive mounts  738  and  740  results in the complementary reciprocating linear motion, such that when drive mount  738  is moving in an upward linear direction, drive mount  740  is moving in a downward linear direction. Thus, with the polishing belt  710  properly positioned between a supply spool and a receive spool (not shown), this movement of the drive mounts  738  and  740  will result in the bidirectional linear movement according to the present invention. Since the support mechanism supports the polishing belt from the backside, and the polishing side, or front side, does not contact the support mechanism, sources of friction other than the wafer that is being polished are minimized from the polishing side of the pad. Thus, polishing side of the pad is not degraded by the support mechanism.  
         [0046]    [0046]FIGS. 8A and 8B illustrate side and cross sectional views, respectively, of a specific implementation of the drive mechanism described above with respect to FIG. 7 in accordance with the present invention.  
         [0047]    The polishing apparatus  800  includes a driving mechanism having a bi-directional linear, or reverse linear, polishing belt  810  for polishing a wafer (not shown) that is supported by the wafer housing (not shown). A processing area  816  has a section of the polishing belt  810  that is supported by a platen  823 , which platen  823  is capable of providing “gimbaling” action for leveling/suspending the section of the polishing belt  810  above it. In addition, an air or magnetic bearing may be positioned underneath the processing area  816  to control the pressure between the section of the polishing belt  810  and the wafer surface during the polishing process.  
         [0048]    Besides the processing area  816 , the polishing apparatus  800  includes in its top portion a supply spool  811 , a receiving spool  815 , and a polishing belt support mechanism  812 , shown as rollers  812   a ,  812   b ,  812   c ,  812   d ,  812   e ,  812   f ,  812   g ,  812   h . Rollers  812   a ,  812   d ,  812   e  and  812   h  are fixed in position, whereas roller pairs  812   b  and  812   c , as well as  812   f  and  812   g , are attached to respective drive supports  820  and  822 , which are each moved in a complementary reciprocating linear motion that is obtained using a driving mechanism  830 . The drive mechanism includes a motor  832 , which, via a belt  834  drives axle  836 , which in turn will rotate each of the two drive mounts  838  and  840 , which in turn provide movement to the elbows  842  and  844 , respectively. Each end of the elbows  842  and  844  can rotate about the respective pivot points such as pivot points  842   a  and  842   b  illustrated in FIG. 8B.  
         [0049]    With the polishing belt  810  fed between the supply spool  811  and the receiving spool  815 , it is apparent that a frontside of the polishing belt  810  will only contact a surface of the wafer or workpiece being polished, while the backside of the polishing belt will be in contact with various surfaces to ensure alignment, including the various rollers  812  described above.  
         [0050]    As is apparent, rotation of the axle associated with motor  832  will cause rotation of the belt  834  and the corresponding axle  836 , and rotation of the two drive mounts  838  and  840 . To each of these drive mounts is attached one of the elbows  842  and  844 , which attachments are preferably 180 degrees out of phase. Rotation of the drive mounts  838  and  840  results in the complementary reciprocating linear motion, such that when drive support  820  is moving in an upward linear direction, drive support  822  is moving in a downward linear direction. Thus, with the polishing belt  810  properly positioned between the supply spool  811  and the receive spool  815  and attached, via roller pairs  812   b ,  812   c  and  812   f ,  812   g  to the drive supports  820  and  822 , respectively, this movement of the drive supports  820  and  822  will result in the bidirectional linear movement according to the present invention.  
         [0051]    Advancing the polishing belt  810 , whether that advancement takes place in incremental step portion movement or in larger step portion movement, whether that movement is while the polishing belt  810  is polishing a wafer or between times that polishing belt  810  is polishing a wafer, will allow for a new portion of the polishing belt  810  to come off of the supply spool  811  and a previously used portion to be taken up by the receiving spool  815 . The mechanism used to implement this movement is preferably the same clutch mechanism as described above with respect to FIG. 5.  
         [0052]    While this embodiment is described using a different drive mechanism than the drive mechanism illustrated in FIG. 5, it should be understood that either of these or other drive mechanisms can be used in accordance with the invention. It is understood that the second embodiments of the present invention with receiving and supply spools can use various numbers of rollers, various types of drive mechanisms, and the like, which cooperate to provide the bidirectional linear or reciprocating motion and is intended to be within the spirit and scope of the present invention. In addition, other similar components/devices may be substituted for the ones described above.  
         [0053]    In addition, the layout or geometry of the polishing pad/belt with respect to the wafer as illustrated in the first and second embodiments can be changed from those illustrated herein to other positions. For example, one can position the polishing pad/belt above the wafer, position the polishing pad/belt vertically with respect to the wafer, etc.  
         [0054]    It is to be understood that in the foregoing discussion and appended claims, the terms “wafer surface” and “surface of the wafer” include, but are not limited to, the surface of the wafer prior to processing and the surface of any layer formed on the wafer, including conductors, oxidized metals, oxides, spin-on glass, ceramics, etc.  
         [0055]    Although various preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and/or substitutions are possible without departing from the scope and spirit of the present invention as disclosed in the claims.