Abstract:
A pad cleaning device ( 210, 220, 250 ) is used in conjunction with spray rinse water to thoroughly clean a polishing pad ( 110 ) of a chemical-mechanical polishing system ( 100 ) after a wafer ( 120 ) has been polished. A sprayer or sprayer extension ( 210, 220, 250 ) is strategically positioned and securely retained on a portion of the dispensing arm ( 130 ) and adapted for applying a rinse water spray directly to the center portion ( 150 ) of the pad preventing conglomerated slurry from accumulating.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to chemical mechanical polishing and, more particularly, to polishing pad cleaner for in-situ cleaning.  
       BACKGROUND OF THE INVENTION  
       [0002]     CMP is a process for improving the surface planarity of a semiconductor wafer and involves the use of mechanical pad polishing systems usually with a silica-based slurry. CMP offers a practical approach for achieving the important advantage of overall wafer planarity.  
         [0003]     CMP systems place a semiconductor wafer in contact with a polishing pad that rotates relative to the semiconductor wafer. The semiconductor wafer may be stationary, or it may also rotate on a carrier that holds the wafer. Problems of conventional methods of performing a chemical mechanical polish is that they produce nonuniform wafers and produce larger than desirable edge exclusion areas. Both of these problems impair operation of resulting electronic components formed from the semiconductor devices. Semiconductor wafer non-uniformity may cause undesirable layers not to be removed at some places and desirable layers to be removed at other places on the wafer surface. This causes various areas on the wafer surface to be unusable for forming semiconductor devices. Process uniformity from wafer to wafer is also important in CMP processing. Known CMP systems, however, suffer from significant wafer-to-wafer non-uniformities. This can also adversely affect the throughput and yield of the CMP process. To achieve a low defect rate, each successive substrate should be polished under similar conditions.  
         [0004]     Another limitation of existing CMP systems relates to a part of the system known as the CMP polish pad. The silica-based slurry is applied to the CMP polish pad to lubricate the interface between the wafer and the CMP polish pad. The slurry also serves the function, because of its silica content, of mildly abrading or affecting the surface of the semiconductor wafer. Relative motion of the polishing pad with respect to the wafer effectuates polishing of the wafer through mechanical abrasion and chemical etching. The amount of mechanical abrasion is determined in part by the size of the abrasive particles in the slurry. Often, during the polishing process, the particles conglomerate forming larger particles which can scratch or otherwise effect the polishing. Changes in the slurry solution properties, such as the particle sizes, have a profound effect on the polishing chemistry and relative removal rates of dielectric films if not properly removed from the pad.  
         [0005]     One of the factors that is accounted for in returning the polishing pad to its condition prior to the polishing of another wafer is the removal from the polishing pad of the debris, such as conglomerated slurry, created during the polishing period. These debris may be on the surface of the polishing pad or trapped within grooves of the polishing pad. If the debris are left on and within the pad, the polishing conditions for the next wafer to be polished will be different from the previous wafer that was just polished.  
         [0006]     A typical method of removing the debris from the polishing pad after a wafer has been polished is to employ a spray rinse over a portion of the surface of the polishing pad. The spray rinse provides a de-ionized water to the pad in hopes of washing away all the debris from the polishing pad following a wafer polishing phase. In another approach, described in U.S. Pat. No. 6,224,470, a pad cleaning brush is used in conjunction with spray rinse water. Although conventional spray rinse approaches and the above-mentioned cleaning brush apparatus provide some measure of cleaning to the polishing pad, some debris can remain behind within the center area of the polishing pad.  
       SUMMARY  
       [0007]     The present invention achieves technical advantages as an apparatus and system used in conjunction with rinse water to thoroughly clean a polishing pad of a chemical-mechanical polishing apparatus after a wafer has been polished. A sprayer or sprayer extension is strategically positioned and securely retained on a portion of the dispensing arm and adapted for applying a rinse water spray directly to the center portion of the pad preventing conglomerated slurry from accumulating.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     For a more complete understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings wherein:  
         [0009]      FIG. 1  illustrates a conventional chemical-mechanical polishing system  100 ; and  
         [0010]      FIGS. 2A-2C  illustrate spray extensions in accordance with exemplary embodiments of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0011]     The numerous innovative teachings of the present application will be described with particular reference to the presently preferred exemplary embodiments. However, it should be understood that this class of embodiments provides only a few examples of the many advantageous uses and innovative teachings herein. In general, statements made in the specification of the present application do not necessarily delimit any of the various claimed inventions. Moreover, some statements may apply to some inventive features, but not to others. Throughout the drawings, it is noted that the same reference numerals or letters will be used to designate like or equivalent elements having the same function. Detailed descriptions of known functions and constructions unnecessarily obscuring the subject matter of the present invention have been omitted for clarity.  
         [0012]     Referring now to  FIG. 1  there is shown a conventional chemical-mechanical polishing system  100  that employs a polishing pad cleaning device. The cleaning device  100  includes a rotatable (rotation direction is shown by the arrow) platen on which a polishing pad  110  is disposed. A drive device is adapted for and used to bring a wafer  120  into mechanical contact with the pad  110  and rotate the wafer  120  in the opposite direction. During a polishing operation, the device may also move the wafer  120  in a linear motion across the surface of the polishing pad  110  in which a portion of the wafer  120  is in mechanical contact with the center most portion of the pad  110 . The wafer  120  is pressed against the pad  110  at a predetermined pressure. During polishing, a slurry is dispensed in droplets onto the surface of the pad  110  to effectuated the chemical mechanical removal of materials from the wafer  120  surface.  
         [0013]     The slurry composition and the pressure applied between the wafer surface and the polishing pad  110  determine the rate of polishing or material removal from the wafer surface. A slurry composition typically includes a colloidal suspension of oxide particles suspended in an alkali solution. Other abrasive components such as ceria suspensions may also be used. During a CMP process, a large volume of a slurry composition is delivered by a dispensing arm  130  positioned over the surface of the polishing pad  110  as the pad  110  is rotated.  
         [0014]     After the wafer  120  has been polished and moved to the next station or from the CMP apparatus  100 , the polishing pad  110  is cleaned by a spray of de-ionized water. Typically the dispensing arm  130  is also used to deliver the spray. Conventionally, the spray is delivered by several nozzles forming a typical spray pattern shown as item  140 . The centrifugal force from the rotation and the de-ionized water are cooperable for carrying away the debris from the polishing pad  110 . Although the typical spray pattern  140  of de-ionized water is adequate to clean most of the debris from a polishing pad, a slurry build-up occurs at the center most portion of the pad  110  of conventional wash approaches. This build-up often includes a conglomeration of the slurry material which is problematic for subsequent polishing of wafers  120  in a sequence process.  
         [0015]     In order to overcome the above-stated concern of cleaning debris more thoroughly from the polishing pad, the present invention provides a spray extension advantageously positioned to thoroughly spray the entire center portion  150  of the pad  110  while the pad is being rotated acting to more thoroughly clean the debris from the polishing pad  110 , wherein the extension further does not interference with other hardware during the process.  
         [0016]     A cross-sectional side view of spray extensions in accordance with exemplary embodiments of the present invention is provided in  FIGS. 2A-2C . Referring now to  FIG. 2A  there is shown a spray extension  210  coupled to a conventional dispensing arm  130  and shown in relation with the center portion  150  of the pad  110 . In this embodiment, the spray extension  210  is adapted to have a profile such that no part of the extension extends over the end of the dispensing arm  130 . Further, the extension is provided with a directional spray nozzle which enables water to be sprayed directly on the pad center  150 .  
         [0017]     Referring now to  FIG. 2B  there is shown another spray extension  220 . In  FIG. 2B , this spray extension  220  extends the nozzle beyond the dispense arm  130  and points the de-ionized water spray directly over the center  150  of the pad. This maximizes the spray force from the fluid velocity in dislodging the slurry conglomerates and cleaning the pad  110 . The water spray angle should be at 90 degrees relative to the pad surface. System  230  allows adjustments to be made on the extension for adequate pad coverage.  
         [0018]     Referring now to  FIG. 2C  there is shown another spray extension  250 . In  FIG. 2C , the extension is another form that allows easy installation by using ‘off the shelf’, currently available components for high purity plumbing. The extension  250  includes a conventional plumbing collar  240  coupling two pieces of pipe such that adjustments can be made on the extension for adequate pad coverage from the water spray. This design also allows optimal cleaning in that the de-ionized water spray from the extension  250  is positioned directly over the pad center  150  to maximize fluid energy.  
         [0019]     Although exemplary embodiments of the invention are described above in detail, this does not limit the scope of the invention, which can be practiced in a variety of embodiments.