Abstract:
A chemical mechanical polishing apparatus comprises a platen having a polishing pad thereon, a wafer carrier holding a wafer on the polishing pad, a washer having a cleaning device; and a dresser. The dresser comprises a bottom disk contacting the polishing pad. The dresser can move between the polishing pad and the washer. When the dresser moves into the washer, a diamond zone on the bottom disk cleans the polishing pad, and the cleaning device cleans the diamond zone.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to a chemical mechanical polishing (CMP) apparatus. In particular, the present invention relates to a washer for the CMP apparatus. 
     2. Description of the Related Art 
     A process commonly used in fabrication of integrated circuits to create a planar topography is chemical mechanical polishing (CMP) process. This process involves chemically removing a surface while also mechanically grinding or polishing it. The combined action of surface chemical reaction and mechanical polishing allows for a controlled, layer by layer removal of a desired material from the wafer surface, resulting in a preferential removal of protruding surface topography and a planarized wafer surface. 
     However, if the CMP process is out of control, the wafer&#39;s surface becomes non-uniform. For an etching process, if contact windows or via holes are formed on a substrate with a non-uniform level, the endpoint of the etching process is not easy to maintain. Some contact windows or via holes may be overetched; some contact windows or via holes may not reach the predetermined depth and thereby experience open circuits. For a lithography process, the accuracy of the exposure is easily lost. With the increase of integration, elements are shrunk and it is important to smooth the substrate surface to a uniform level. 
     FIG. 1 schematically illustrates a conventional CMP apparatus  100  with a platen  110 , a dresser  120 , a wafer carrier  150 , and a washer  160 . 
     Referring to FIG. 2, a polishing pad  112  of polyester is positioned on the platen  110 , and a slurry is positioned on the polishing pad  112 . The wafer carrier  150  includes a guide ring  152 , a top ring  154  and a backing ring  156 . The top ring  154  is supported on the backing ring  156 . The guide ring  152  is positioned on the outer periphery of the top ring  154  to surround wafer  102  so that the wafer  102  is not disengaged from the wafer carrier  150 . The wafer is polished while being pressed between the wafer carrier  150  and the platen  110 . 
     After polishing, the polishing pad  112  is washed by the dresser  120 . However, some residue, from the reactant of the slurry and the removed surface layer, still remains on the polishing pad  112 . If the residue is not removed, it can damage the resulting polished wafer. 
     FIG. 3 shows the top view of the CMP apparatus. After removing the wafer  102  from the platen  110  by the wafer carrier  150 , the dresser  120  is moved on the platen  110  and the polishing pad  112  is cleaned by clockwise or counterclockwise action of the dresser  120 . The residue in the polishing pad  112  is scraped by the dresser  120  every one or several turns of the CMP process. The dresser  120  is then washed by immersion in the washer  160  filled with water to remove the residue attached to a bottom disk  125  of the dresser  120 . The dresser  120  rotates in the washer  160  to make water flow. The flowing water removes the residue. 
     However, using the flowing water to remove all of the residue is difficult. Conventionally, the bottom disk  125  is frequently changed by shutting down the CMP apparatus, to prevent the residue from damaging the wafers. 
     SUMMARY OF THE INVENTION 
     The present invention provides a CMP apparatus comprising a platen, a wafer carrier, a washer with a cleaning device, and a dresser. A polishing pad is disposed on the platen. The wafer carrier holds a wafer on the polishing pad, and the wafer carrier can move on to and off of the polishing pad. The dresser has a bottom disk contacting the polishing pad, and can move between the polishing pad and the washer. A diamond zone disposed on the bottom disk can clean the polishing pad, and the cleaning device can clean the diamond zone. 
     The cleaning device can be at least one scrubber disposed in the lower part of the washer, or an ultrasonic device, or combination thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, given by way of illustration only and thus not intended to be limitative of the present invention. 
     FIG. 1 is a CMP apparatus according to the prior art. 
     FIG. 2 is a lateral view of the CMP apparatus of FIG.  1 . 
     FIG. 3 is a top view of the CMP apparatus of FIG.  1 . 
     FIG.  4 ( a ) is a lateral view of a dresser according to the prior art, and FIGS.  4 ( b ) and ( c ) are top views of the dresser. 
     FIG. 5 shows the bottom disk and the embedded diamonds of the dresser, and some residue remaining in the space between the diamonds. 
     FIGS.  6 ( a )- 6 ( c ) show a washer according to the first embodiment of the present invention. 
     FIG. 7 shows a washer according to the second embodiment of the present invention. 
     FIG. 8 shows a washer according to the third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides a washer  160  for the dresser  120  of CMP apparatus  100 . The dresser  120  is used to scrape the residue from the polishing pad  112 . The dresser  120  can be a brush or diamond disk. In this embodiment, the dresser  120  uses diamond disk as an example. 
     Referring to FIG.  4 ( a ), the dresser  120  comprises the bottom disk  125  and the revolving spindle  123  connecting to the bottom disk  125 . The bottom disk  125  and the revolving spindle  123  are metal. The surface of the bottom disk  125  is treated by special technique and embedded with diamonds. The bottom disk  125  has two types, one is shown in FIG.  4 ( b ), the outside lane is a diamond zone  126  uniformly embedded with a plurality of diamonds  124 . Another bottom disk  125  is shown in FIG.  4 ( c ), the outside lane a diamond zone  126  with several diamond dishes  127 . The diamond dishes  127  are detachable, and embedded with 10˜30 diamonds. The diameter of these diamonds  124 , no matter which type, is about 50˜200 μm. The density of these diamonds  124  is about 2˜100 pcs/mm 2 . 
     FIG. 5 shows the bottom disk  125  and the embedded diamonds  124  of the dresser  120 . After cleaning the polishing pad  112 , some residue  136  remains in the space between the diamonds  124 . It is difficult to remove the residue  136 , especially by the dresser  120 . If the residue  136  remaining in the space between the diamonds  124  is not removed, the cleaning efficiency of the dresser  120  is reduced. Residue  136  remaining in the polishing pad  112  contaminates the wafer to be polished. 
     FIG. 6 shows a washer  160  according to the first embodiment of the present invention. As shown in FIG.  6 ( a ), a scrubber  130  is disposed in the lower part of the washer  160 . The length and width of the scrubber  130  must cover the width of the diamond zone  126  in the bottom disk  125  of the dresser  120 . When the dresser spins, the scrubber  130  cleans the whole diamond zone  126 . Therefore, the size of the scrubber  130  depends on the size of the bottom disk  125  and the width of the diamond zone  126 . 
     As shown in FIG.  6 ( b ), two scrubbers  130  are set in the lower part and at two sides of the washer  160  to enhance the cleaning efficiency. The length and the width of these two scrubbers  130  depends on the size of the bottom disk  125  and the width of the diamond zone  126 . The number of the scrubbers  130  is not limited to one and two. The number of the scrubbers  130  and the position of the scrubbers  130  can be altered as needed. 
     FIG.  6 ( c ) shows a cross-section of A—A line in FIGS.  6 ( a ) and ( b ). The scrubber  130  comprises a base  134  and brushes  132  fixed at the base  134 . The base  134  can be metal. The brushes  132  can be synthetic resin or other soft and elastic materials, which can protect the surface of the dresser  120  and prevent other impurities. The diameter of the brushes  132  is about 20˜250 g m. The gap between the brushes  132  is about 0.3˜1.5 mm. The length of the brushes  132  must be maintained to contact the space between the diamonds  124 . The base  134  of the scrubber  130  connects with a hoist  166 . The height of the base  132  is held by the hoist  166  through a controller  168 . If the cleaning efficiency for the dresser  120  is not good, the scrubber  130  is lifted by adjusting the controller  168  so as to enhance the pressure of the brushes  132  to the diamond zone  126  by enhancing the contacting length of the brushes  132 . If the cleaning efficiency for the dresser  120  is adequate, the scrubber  130  is lowered to reduce the pressure of the brushes  132  to the diamond zone  126 , and the lifetime of the brushes  132  is then increased. 
     A liquid  128  fills the washer  160 . The liquid  128  can be water or other solvents. The liquid  128  is injected from an input  162  and discharged through an exhaust. The level of the liquid  128  must maintain a consistent height to stabilize the cleaning efficiency. When the dresser  120  spins in the washer  160 , the residue  136  is scraped by the brushes  132  and falls into the liquid  128 . The residue  136  is then removed by the flowing liquid  128  through the exhaust  164 . The washing time depends on the amount of residue  136  remaining in the diamond zone  126 . 
     FIG. 7 shows a washer  160  according to the second embodiment of the present invention. An ultrasonic device  140  is set in the washer  160 . A liquid  128  fills the washer  160 . The liquid  128  can be water or other solvents. The liquid  128  is injected from an input  162  and discharged through an exhaust. The ultrasonic device  140  produces a mass of bubbles to agitate the residue  136  existing in the space between the diamonds  124  of the bottom disk  125  of the dresser  120 , and dislodge the residue  136 . The residue  136  is then removed by the flowing liquid  128  through the exhaust  164 . The level of the liquid  128  must maintain a consistent height to stabilize the cleaning efficiency. The washing time depends on the amount of residue  136  existing in the diamond zone  126 , preferably about 10˜60 seconds. The ultrasonic device  160  can be used to clean any type of dresser, such as brush type dresser. 
     FIG. 8 shows a washer  160  according to the third embodiment of the present invention. A scrubber  130  is disposed in the lower part of the washer  160 . The length and width of the scrubber  130  must cover the width of the diamond zone  126  in the bottom disk  125  of the dresser  120 . When the dresser spins, the scrubber  130  cleans the whole diamond zone  126 . The base  134  of the scrubber  130  connects to a hoist  166 . The height of the base  132  is maintained by the hoist  166  through a controller  168 . If the cleaning efficiency for the dresser  120  is inadequate, the scrubber  130  is lifted by adjusting the controller  168  so as to enhance the pressure of the brushes  132  on the diamond zone  126  by enhancing the contact length of the brushes  132 . If the cleaning efficiency for the dresser  120  is adequate, the scrubber  130  is lowered to reduce the pressure of the brushes  132  on the diamond zone  126 , and the lifetime of the brushes  132  is then increased. 
     In the third embodiment, not only the scrubber  130 , but also the ultrasonic device  140 , is used to clean the dresser  120 . The ultrasonic device  140  produces a mass of bubbles to agitate the residue  136  existing in the space between the diamonds  124  of the bottom disk  125  of the dresser  120 , and dislodge the residue  136 . The residue  136  is then removed by the flowing liquid  128  through the exhaust  164 . 
     The residue  136  is scraped by the scrubber  130  and agitated by the ultrasonic device  140  at the same time to thoroughly clean the bottom disk  125  of the dresser  120 . 
     A liquid  128  fills the washer  160 . The liquid  128  can be water or other solvents. The liquid  128  is injected from an input  162  and discharged through an exhaust  164 . The residue  136  is scraped by the scrubber  130  and agitated by the ultrasonic device  140  and falls into the liquid  128 . Moreover, residue  136  remaining in the brushes  132  can also be removed by the ultrasonic device  140 . The residue  136  is then removed by the flowing liquid  128  through the exhaust  164 . 
     The foregoing description of the preferred embodiments of this invention has been presented for purposes of illustration and description. Obvious modifications or variations are possible in light of the above teaching. The embodiments were chosen and described to provide the best illustration of the principles of this invention and its practical application to thereby enable those skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.