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  Single-layer polishing padUSPTO Application #: 20080102741Title: Single-layer polishing pad Abstract: A foamed plastic is cut to form a single-layer polishing pad having a desired rigidity and compressibility. A polishing surface of the polishing pad has a higher density than a mounting surface of the polishing pad. The polishing surface and the mounting surface may have different areas having different densities for achieving desired rigidity and compressibility property. Furthermore, methods of making such single-layer polishing pads are also disclosed. (end of abstract) Agent: Pai Patent & Trademark Law Firm - Seattle, WA, US Inventors: Wen-Chang Shih, Yung-Chung Chang, Min-Kuei Chu USPTO Applicaton #: 20080102741 - Class: 451527000 (USPTO) Related Patent Categories: Abrading, Flexible-member Tool, Per Se, Interrupted Or Composite Work Face (e.g., Cracked, Nonplanar, Etc.) The Patent Description & Claims data below is from USPTO Patent Application 20080102741. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application is a divisional application of U.S. patent application Ser. No. 11/459,352, filed Jul. 22, 2006, presently pending, which in turn is a divisional application of U.S. patent application Ser. No. 10/908,232, filed May 3, 2005, now Pat. No. 7,101,501, which in turn claims the priority benefit of U.S. Provisional Application No. 60/521,483, filed May 5, 2004 and U.S. Provisional Application No. 60/521,740, filed Jun. 29, 2004. All of these applications are incorporated herein by this reference. BACKGROUND [0002] 1. Field of Invention [0003] The present invention relates to a polishing apparatus and manufacturing method thereof. More particularly, the present invention relates to a single-layer polishing pad and a method of producing the same. [0004] 2. Description of Related Art [0005] During the manufacturing process of semiconductor integrated circuits, isolation structures, metal lines and dielectric layers are stacked layer by layer, and the surface of a wafer is thus less and less planar. Limited by the focus depth of an exposing machine, pattern transferal from a photomask to a photoresist layer is increasingly difficult, and the exposed pattern of the photoresist layer is increasingly distorted. Chemical mechanical polishing (CMP) is the only true global planarization process to resolve the problem mentioned above. [0006] In CMP, a wafer is pressed against on a polishing pad to allow movement of the wafer on the polishing pad having polishing slurry thereon. The polishing slurry contains fine abrasive particles and a chemical reagent. Both the wafer and the polishing pad are rotated automatically; hence the wafer is planarized by mechanical polishing by the abrasive particles and chemical reaction of the chemical reagent. [0007] An important goal of CMP is achieving uniform planarity of the wafer surface, and the uniform planarity also has to be achieved for a series of wafers processed in a batch. The rigidity (or stiffness) and the compressibility (or compliance) of a polishing pad have great influence on the planarity of the polished wafer. Generally speaking, a polishing pad with higher rigidity can increase the polishing planarity of the polished wafer, and a polishing pad with higher compressibility can increase the polishing uniformity of the polished wafer. Therefore, a wafer polished by a rigid polishing pad often needs to be further polished by a soft polishing pad to improve the polishing uniformity. The CMP process thus suffers from low throughput. [0008] Conventionally, to satisfy both the planarity and the uniformity requirements of the CMP process, at least a layer of rigid pad and at least a layer of soft pad are stacked to form a desired composite polishing pad, such as the polishing pads disclosed by U.S. Pat. No. 5,212,910 and U.S. Pat. No. 5,257,478. As stated in U.S. Pat. No. 6,217,426, although a composite polishing pad can partially satisfy both the planarity and the uniformity requirements of the CMP process, some other problems are also produced. For example, pressure transmission is different for a rigid pad and a soft pad, and the polishing uniformity can sometimes be poor. Furthermore, a greater number of layers stacked in a composite polishing pad creates more variables that can affect the rigidity and compressibility of the composite polishing pad. Hence, the polishing planarity and uniformity are more difficult to control. [0009] Besides, if the two pads in a composite polishing pad are not adhered well enough, the composite polishing pad may easily delaminate during the polishing process. Therefore, U.S. Pat. No. 6,217,426 discloses a polishing pad having a pattern of protrusions on the mounting surface of the polishing pad to limit the pressure transmission area and increase compressibility of the polishing pad. [0010] In the prior art described above, the cost and complexity in producing a polishing pad are unavoidably increased. SUMMARY [0011] In one aspect, the present invention provides a single-layer polishing pad having desired rigidity and compressibility to meet the requirements of polishing planarity and uniformity. [0012] In another aspect, the present invention provides a method of producing a single-layer polishing pad having desired rigidity and compressibility. The method utilizes the pore-size-distribution property in a porous polymer to control the rigidity and compressibility of a polishing pad. [0013] In accordance with the foregoing and other aspects of the present invention, a single-layer polishing pad is provided. The single-layer polishing pad comprises a body, a polishing surface on one side of the body, and a mounting surface on the other side of the body. The body is made of a porous polymer, and the density of the polishing surface and the density of the mounting surface are different. [0014] In a preferred embodiment of the present invention, the density of the polishing surface is higher than the density of the mounting surface. [0015] In another preferred embodiment, the polishing surface has at least a first area and at least a second area, and the density of the first area is higher than the density of the second area. [0016] In yet another preferred embodiment, the mounting surface has at least a third area and at least a fourth area, and the density of the third area is higher than the density of the fourth area. [0017] In yet another preferred embodiment, the single-layer polishing pad comprises a polishing surface, a mounting surface, and a central part between the polishing surface and the mounting surface, and the porosity of the central part is higher than the porosity of the polishing surface. [0018] In accordance with the foregoing and other aspects of the present invention, a method of producing a single-layer polishing pad is provided. A foamed pad is formed by a foam process, and the foamed pad has a first planar surface and a second planar surface. A third planar surface is formed by removing the first planar surface. The density of the second planar surface, which serves as a polishing surface, is higher than the density of the third planar surface, which serves as a mounting surface. [0019] In accordance with the foregoing and other aspects of the present invention, a method of producing a single-layer polishing pad is provided. A foamed pad is formed by a foam process. The foamed pad has at least a first region and at least a second region, and the thickness of the first region is larger than the thickness of the second region. A first planar surface is formed by removing a surface of the foamed pad. The density of the first planar surface on the first region is lower than the density of the first planar surface on the second region. [0020] In a preferred embodiment, a second planar surface is formed by removing the other surface of the foamed pad. [0021] In the foregoing, a pore-size-distribution property in a porous polymer is utilized to produce a single-layer polishing pad having two surfaces with uniform rigidity or various rigidities. Therefore, not only can the requirements for lower cost and higher CMP process throughput be achieved, but also the polishing planarity and uniformity can be achieved. Continue reading... Full patent description for Single-layer polishing pad Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Single-layer polishing pad 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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