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  Polishing device and methodUSPTO Application #: 20070270087Title: Polishing device and method Abstract: A polishing device includes a polishing head for pressing and holding a semiconductor wafer, a pair of polishing pads having the same diameter as the polishing head for polishing the semiconductor wafer, and a subordinate polishing pad having a smaller diameter for polishing a peripheral portion of the semiconductor wafer. Both the pair of polishing pads are rotated in one direction, or in opposite directions. The rotational speed of the first and/or second polishing pad is controlled so that an equal polishing rate is obtained for the first and second polishing pads when the polishing pads are rotated in opposite directions. (end of abstract) Agent: Sughrue Mion, PLLC - Washington, DC, US Inventor: Toshiya Saito USPTO Applicaton #: 20070270087 - Class: 451 41 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070270087. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]The present invention relates to polishing device and method. In particular, the present invention relates to an improvement of the polishing device and method generally used for polishing a wafer. [0003]2. Description of the Related Art [0004]Along with development of a finer design rule in the semiconductor fabrication process, a higher degree of flatness is requested for the surface of a semiconductor wafer in each step of the process for manufacturing semiconductor devices. [0005]For achieving a flat surface of the film on the wafer, attempts have been made to satisfy the requested degree of flatness by improving the flatness of the surface of the as-deposited film itself, and by using a reflow technique such as annealing coated films including a SOG (spin on glass) film and a BPSG (borophospho-silicate glass) film at a high temperature. The CMP technique, which directly polishes the surface of the semiconductor wafer, has been increasingly used since the design rule for the semiconductor device was settled at as low as 0.35 micrometers or smaller. [0006]The CMP process is generally effective for eliminating the step difference on the surface of the semiconductor wafer; however, causes a relatively poor within wafer uniformity in a larger wafer area after the polishing. In recent years, semiconductor devices are fabricated on a larger-diameter wafer having a diameter of 300 mm, for example. This necessitates a further improvement of the within wafer uniformity of the polished film. The polishing device using the CMP process is described, for example, in Patent Publications JP2003-521117A and JP-2001-25962A. [0007]The conventional polishing device will be described with reference to the accompanying drawings. FIGS. 5 and 6 show a sectional view and a top plan view, respectively, of a typical conventional polishing device. The polishing device, generally designated at numeral 100, basically includes a polishing head 11, a polishing pad 15, a dresser 18, and a slurry supply nozzle 17. The polishing head 11 holds a semiconductor wafer 12 while pressing the semiconductor wafer 12 on the rear surface thereof. The polishing pad 15 polishes the main surface of the semiconductor wafer 12. The dresser 18 carries out a dressing treatment of the front surface of the polishing pad 15. The slurry supply nozzle 17 supplies slurry including an abrasive between the polishing pad 15 and the semiconductor wafer 12. [0008]The polishing head 11 presses the semiconductor wafer 12 at the rear surface thereof by using a membrane sheet 14 while retaining the semiconductor wafer 12 in the in-plane direction of the wafer by using a retainer ring 13, whereby rotation of the polishing head 11 rotates the semiconductor wafer 12. The polishing pad 15 polishes the main surface of the semiconductor wafer 12 while, for example, rotating in the same direction as the semiconductor wafer 12. During this polishing treatment, slurry including an abrasive is supplied between the polishing pad 15 and the main surface of the semiconductor wafer 12 from the slurry supply nozzle 17. The slurry spreads uniformly on the front surface of the polishing pad 15 by rotation of the polishing pad 15, whereby the polishing of wafer is performed under the continuous supply of the slurry. If a groove formed on the polishing pad 15 is clogged during the polishing of the wafer, the dresser 18 is activated to perform the dressing treatment on the surface of the polishing pad 15. A periphery pressing member 16 presses the peripheral portion of the wafer 12 to achieve a desired within wafer uniformity, which is likely to be lost particularly in the vicinity of the periphery of the wafer. [0009]The polishing pad 15 is driven for the rotational movement thereof during polishing the wafer, as described above. During the polishing treatment, the center of the polishing pad 15 remains stationary to have a polishing rate of zero. For this reason, the polishing of the semiconductor wafer 12 is performed radially outside the center of the polishing pad 15. Therefore, the diameter of the polishing pad 15 is twice as large as or larger than the diameter of the polishing head 11 which has almost the same diameter as the semiconductor wafer 12. That is, the effective processing area of the polishing pad 15 used for polishing the semiconductor wafer 12 is equal to or less than 25% of the total area of the polishing pad 15. [0010]The smaller ratio of the effective polishing area to the total area of the polishing pad inevitably increases the actual size of the polishing pad, thereby increasing the cost for the CMP process. [0011]In addition, the dresser is used in order to achieve a stable within wafer uniformity of the polishing rate in the CMP process. The larger size of the polishing pad involves a difficulty in achieving the stable dressing treatment and increases the number of times of the dressing treatment. The larger number of times of the dressing treatment reduces the lifetime of the dresser to further increase the cost for the CMP process. [0012]Further, in the CMP process, the polishing pad and the slurry are generally selected depending on the target thin film to be polished. Each time such selection is made, the wafer is transferred to another polishing device which is suited or dedicated to the material of the thin film to be polished. Due to the time length required for such transfer of the wafer, the throughput of the fabrication process of the semiconductor device is lowered. Further, the within wafer uniformity of the film thickness after polishing by the CMP is particularly lower in the vicinity of the periphery of the wafer. Therefore, only an adjustment of the load by using the periphery pressing member in the polishing head is insufficient for achieving the required within wafer uniformity. SUMMARY OF THE INVENTION [0013]In view of the problem of the conventional polishing device and polishing process as described above, it is an object of the present invention to provide a polishing device and a polishing method which are capable of reducing the cost for the CMP process. [0014]The present invention provides a polishing device including: a polishing head that holds a wafer while allowing rotation thereof; and first and second polishing pads juxtaposed with each other in contact with a surface of the wafer held by the polishing head. [0015]The present invention also provides method for polishing a wafer by using the above polishing device, the method including a first step including concurrent steps of rotating the first polishing pad, supplying slurry onto a surface of the first polishing pad, stopping rotation of the second polishing pad and supplying water onto a surface of the second polishing head. [0016]The present invention further provides a method for polishing a wafer by using the polishing device according to claim 1, the method including a first step including concurrent steps of rotating the first and second polishing pads, and supplying slurry onto a surface of the first and second polishing pads. [0017]The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0018]FIG. 1 is a sectional view of a polishing device according to an exemplary embodiment of the present invention; [0019]FIG. 2 is a top plan view of the polishing device of FIG. 1; [0020]FIG. 3 is a sectional view showing the state of polishing the wafer at the periphery thereof by using the polishing pad having a small diameter; [0021]FIG. 4 is a top plan view of a polishing device according to a first modification of the above embodiment; Continue reading... Full patent description for Polishing device and method Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Polishing device and method patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Polishing device and method or other areas of interest. ### Previous Patent Application: Chemical mechanical polishing slurry, cmp process and electronic device process Next Patent Application: Grill and griddle cleaning device Industry Class: Abrading ### FreshPatents.com Support Thank you for viewing the Polishing device and method patent info. IP-related news and info Results in 7.16689 seconds Other interesting Feshpatents.com categories: Accenture , Agouron Pharmaceuticals , Amgen , AT&T , Bausch & Lomb , Callaway Golf |
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