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  Carrier for double side polishingUSPTO Application #: 20060128276Title: Carrier for double side polishing Abstract: In a carrier of the invention, a thick ring-shaped support frame is provided at an outer periphery of a carrier body in which a workpiece housing hole for holding a workpiece is opened. An outer periphery of the support frame is provided with a teeth portion for engaging with driving gears for driving the carrier. The support frame is made of a different member from the carrier body. The carrier body is removably attached to the support frame by screws. The carrier body is made of a material suitable for holding a wafer. The support frame is made of a material suitable for engaging with driving gears for moving the carrier. (end of abstract)
Agent: Pillsbury Winthrop Shaw Pittman, LLP - Mclean, VA, US Inventors: Akira Horiguchi, Shoji Nakao USPTO Applicaton #: 20060128276 - Class: 451041000 (USPTO) Related Patent Categories: Abrading, Abrading Process, Glass Or Stone Abrading The Patent Description & Claims data below is from USPTO Patent Application 20060128276. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The invention relates to a double side polishing carrier suitably used for polishing both sides of a semiconductor wafer as a raw material of a semiconductor device. Specifically, the invention relates to a double side polishing carrier suitably used in a single wafer type double side polisher. [0003] Priority is claimed on Japanese Patent Application No. 2004-358247, filed Dec. 10, 2004, the content of which is incorporated herein by reference. [0004] 2. Description of the Related Art [0005] A double side polisher having a planetary gear mechanism has frequently been used for double side polishing of semiconductor wafers. The planetary gear type double side polisher is a kind of batch processing apparatus in which both sides of a plurality of wafers are polished simultaneously. In this type of double side polisher, a plurality of carriers are arranged about the rotating center of upper and lower rotating surface plates. Each of the plurality of carriers has a sufficiently smaller diameter than the surface plates. While holding one or a plurality of wafers, the carrier rotates in an interstitial space between the upper and lower surface plates. Along with rotating, the carrier also revolves around the rotation center of the surface plates. By this epicyclic movement of carriers in the interstitial space between the surface plates, both sides of a wafer held in each carrier are polished. [0006] Recently, the diameter of a semiconductor wafer to be subjected to double side polishing has increased rapidly. Wafers of 300 mm in diameter are already being produced, and production of still larger wafers is expected in the future. A multi-carrier type polisher using a plurality of carriers is not preferable for double side polishing of such a large sized wafer, since the large wafer size requires a large apparatus. In such a large apparatus, a reduction of maintenance performance cannot be avoided. For example, in such a large apparatus, maintaining precision, and general maintenance and inspection of the apparatus are difficult. In addition, in order to satisfy a requirement for a highly flat wafer surface, it is desirable that working conditions for manufacturing wafers are optimized for each single wafer. From such a point of view, a single wafer type polisher is considered as preferable for double side polishing of large sized wafers. [0007] A single wafer type double side polisher is a single carrier type apparatus using a single carrier having a diameter larger than the diameter of upper and lower rotating surface plates. This is the most important characteristic structure of the single wafer type double side polisher. In this polisher, a wafer is held in a carrier having a larger diameter than the wafer. Both sides of the large sized wafer are polished by a circular movement of the carrier in an interstitial space between the upper and lower rotating surface plates. Compared to the multi-carrier type polisher which simultaneously polishes a plurality of wafers held in a plurality of carriers, downsizing and cost reduction can be expected in the single wafer type double side polisher. [0008] Japanese Unexamined Patent Application, First Publication No. 2001-315057 discloses a single wafer type double side polisher. In this apparatus, a carrier holds a wafer in an eccentric position. The carrier is arranged concentrically with the upper and lower surface plates, and rotates around the center axis. By the concentric rotation of the carrier around the center axis of the rotating surface plates, the wafer held in the eccentric position of the carrier revolves around the center of the carrier in an interstitial space between the rotating surface plates. As a result, both sides of the wafer are polished. [0009] Circumferential velocity of a portion of the rotating surface plate increases with distance from the center from zero velocity at the center towards a maximum velocity at the periphery of the rotating surface plate. Therefore, polishing rate by the surface plate also differs significantly between the center portion and peripheral portion of the surface plate. [0010] As exemplified by the apparatus of Japanese Unexamined Patent Application, First Publication No. 2001-315057, the single wafer type double side polisher has a principal structure that uses the entire portion of the surface plates for polishing a single wafer. Therefore, unevenness of polishing caused by an inequality in circumferential velocity of the portion of the surface plate is not negligible. From this point of view, compared to the multi-carrier type double side polisher using a plurality of carriers simultaneously, for example, like the planetary gear type double side polisher, the single wafer type double side polisher is disadvantageous for retaining flatness of a wafer. [0011] In the case of the multi-carrier type double side polisher using a plurality of carriers, the plurality of carriers placed in the interstitial space between the upper and lower surface plates are arranged near the outer periphery of the surface plates. Therefore, the difference of circumferential velocity between the outer portion and inner portion of the surface plate has little influence on the wafer polishing. As a result, along with the effects of revolution and rotation of the carriers, the wafers held in the carriers are evenly polished. [0012] In the practical polishing process by a single wafer type double side polisher, the wafer itself rotates in the carrier. In addition to this effect, as a countermeasure, for example, by supplying more abrasive fluid to the center portion than to the outer portion of the plate, unevenness of the wafer surface is maintained below the value expected from the partial inequality in circumferential velocity of the plate. However, it is still difficult to eliminate the influence of an unequal circumferential velocity of the plate portions, and therefore, it is difficult to ensure a sufficient flatness of the wafer. [0013] In order to avoid the above-described problem of the single wafer type double side polisher, it is effective to mobilize the carrier with complex movement in the interstitial space between the upper and lower surface plates. By this movement, each portion of the carrier moves along a complex locus, and the effect of circumferential velocity of the rotating surface plate applied to each portion of the wafer is equalized. Therefore, the flatness of the wafer is improved. Based on this consideration, the inventors preliminarily disclosed a method and apparatus for double side polishing in Japanese Patent Application No. 2004-127074 (First Publication No. 2005-205585). In this apparatus, a carrier movement includes a circular movement around an eccentric position remote from the center as well as rotation in the circumferential direction. Where necessary, rotating surface plates are moved in a direction perpendicular to their rotation axis. [0014] However, in order to mobilize the carrier with such compound movement including radial movement relative to the surface plates, it is necessary to make the external diameter of the carrier sufficiently greater than the external diameter of the surface plate so that the carrier moving in the radial direction is not completely removed from the interstitial space between the surface plates. For example, to polish a wafer of 300 mm in diameter by a surface plate of 380 mm in diameter, it is necessary to use a carrier having a diameter greater than 500 mm. As a result, overhang of the carrier outside the surface plate is not negligible. The overhanging portion of the carrier is shown as a portion outside the rotating surface plate 50 in FIG. 2. Such an overhanging portion causes a problem as follows. [0015] Compared to the increase in wafer size as a raw material for a semiconductor device, an increase in wafer thickness is restricted to a lower level. A normal thickness of a 300 mm wafer is 0.775 mm. A carrier used to finish the wafer so as to have such thickness generally has a thickness of about 0.75 mm. In order to retain mechanical strength in such a thin and large carrier, the carrier is made of a highly rigid material such as glass fiber-reinforced epoxy resin. [0016] When such a thin but large sized carrier having a gear wheel shape is subjected to a compound movement in an interstitial space between the upper and lower surface plates, the overhanging portion of the carrier is deformed by an external force applied from the outer periphery of the carrier by driving gears. When the carrier is subjected to a running torque by driving gears, the carrier tends to escape towards the thickness direction. As a result, the carrier is subjected to a load in the thickness direction. When most of the portion of the carrier is supported by the upper and lower surface plates, the carrier is not deformed by the load in the thickness direction. However, when the carrier has a significantly larger size than the surface plates, only a central portion of the carrier is supported by the surface plates, and a large unsupported overhanging portion of the carrier is deformed by the load in the thickness direction. As a result, a failure of the carrier occurs frequently. [0017] Furthermore, when the overhanging portion of the carrier is deformed in the thickness direction, the deformed carrier made of a highly rigid material applies a load on the surface plates. Such a load destabilizes the load applied from the surface plates to the wafer, and therefore, reduces the precision of polishing. [0018] In addition, the carrier made of glass fiber-reinforced epoxy resin generates a fine fibrous powder along with the driving of the carrier by driving gears arranged around the outer periphery of the carrier. This fibrous powder also has an adverse effect on the polishing, for example, by cutting flaws on the wafer surface. [0019] When a carrier is used repeatedly, an inner surface of an opening of the carrier is damaged due to friction with a wafer held in the opening. Therefore, the carrier needs to be replaced with a new one after the using several tens of times. However, the conventional type of carrier is relatively expensive, partially because of the necessity of cutting teeth around the carrier. Therefore, frequent changing of the carrier causes an unavoidable increase of running cost of the polisher. [0020] An object of the present invention is to provide a double side polishing carrier (a carrier used for polishing of both sides of workpieces), which can be used for single carrier type double side polisher. By using this carrier, although the carrier has a large diameter and is moved with compound movement including a radial component, deformation of an overhanging portion of the carrier, failure of the carrier caused by the deformation, and reduction of precision in polishing can effectively be prevented. SUMMARY OF THE INVENTION [0021] A double side polishing carrier of the invention is used in a single carrier type double side polisher which moves the carrier with compound movement. The carrier holding a workpiece (for example a wafer) is inserted between upper and lower surface plates of the polisher. The compound movement of the carrier includes a first movement in the circumferential direction, and a second movement having a radial component. By this compound movement, the workpiece held in the carrier is polished. The carrier comprises a disk shape carrier body having at least one opening (workpiece housing hole) for holding the workpiece; and a ring-shaped support frame which is provided at the outer periphery of the carrier body to support the carrier body. The support frame is formed thicker than the carrier body and has teeth in its periphery to engage with driving gears. [0022] Since the double side polishing carrier of the invention is used in the single carrier type and compound movement type double-side polisher, the carrier has a large overhanging portion outside the surface plate. However, in this carrier, at the periphery of the disk shaped carrier body having at least one workpiece housing hole for holding the workpiece, a thick support frame is provided to support the carrier body. Therefore, running torque applied by the driving gear is accepted by the thick support frame, and deformation of the carrier in the thickness direction is restricted. For example, for supporting a carrier body of not more than 1 mm in thickness, a support frame of 10 mm in thickness and 15 mm in radial width from an inner circumferential edge to an outer edge of a tooth (addendum circle) may be used. Continue reading... Full patent description for Carrier for double side polishing Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Carrier for double side polishing 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. 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