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  Semiconductor device and method for manufacturing the semiconductor deviceUSPTO Application #: 20070190908Title: Semiconductor device and method for manufacturing the semiconductor device Abstract: A method is used for manufacturing a semiconductor device including a circuit-fabricated side on which an encapsulation layer is formed. The method includes the following steps. A semiconductor wafer is placed on the suction surface of a suction stage, the suction surface having a diameter in the range of 99 to 100.5% of a diameter of the semiconductor wafer. The semiconductor wafer is held on the suction surface of the suction stage by suction. A back surface of the semiconductor wafer is ground. The back surface of the semiconductor wafer is ground such that a surface roughness of the ground back surface is not greater than 5 nm. The encapsulation layer has a flexural modulus not smaller than 12 Gpa and not larger than 18 Gpa. (end of abstract) Agent: Rabin & Berdo, PC - Washington, DC, US Inventor: Yasuo Tanaka USPTO Applicaton #: 20070190908 - Class: 451 41 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070190908. 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 a semiconductor device and a method for manufacturing the semiconductor device, and more particularly to a method for manufacturing small semiconductor devices such as a wafer level chip size package (WCSP) in which a plurality of circuit elements are formed on a semiconductor wafer and then the semiconductor wafer is sliced into individual dice. [0003]2. Description of the Related Art [0004]Recently, there have been strong demands in the field of electronic equipment towards miniaturized and thinner packages. The thickness of passive components such as capacitors and resistors mounted On a circuit board has been reduced to about 200 .mu.m. This trend has also placed demands on active components such as memories and CPUs having as small a thickness as the capacitors and resistors. [0005]WCSP type semiconductor devices are generally of the construction in which circuits are fabricated on one side of a semiconductor substrate (e.g., Si) and are sealed with a sealing layer of resin. Because the encapsulation layer and the semiconductor substrate have different physical values (primarily thermal expansion coefficient), when they are laminated, the semiconductor substrate tends to extend outward. One problem with grinding a semiconductor wafer at its back side surface is that a thinner wafer causes the semiconductor substrate to tend to extend further outward. [0006]A thin semiconductor wafer may be manufactured by grinding the back surface of the semiconductor wafer while maintaining the semiconductor flat in the following way. A protection tape is attached to the circuit side of the semiconductor wafer. Then, the semiconductor wafer is mounted on a suction stage with the protection tape between the semiconductor wafer and the suction stage. After grinding, the semiconductor wafer is transferred to the next process with the protection tape attached to the semiconductor wafer. Then, a die bonding film is attached to the side of the wafer opposite to the protection tape, and then the protection tape is removed from the semiconductor wafer. In this manner, warpage of a semiconductor wafer is prevented. [0007]Alternatively, a thin semiconductor wafer may be manufactured by grinding the back surface of the semiconductor wafer while maintaining the semiconductor flat in the following way. After coarse grinding, the ground wafer is sucked to a suction pad that is as large as the outer geometry of the wafer, and then the semiconductor wafer is released from the suction stage. Subsequently, the semiconductor wafer is transferred to a fine grinding apparatus. This allows the wafer to be maintained flat during the coarse grinding and fine grinding. In this manner, warpage of a semiconductor wafer after fine grinding may be minimized. [0008]The aforementioned techniques are used for grinding the back surface of a semiconductor device while also maintaining the semiconductor wafer flat, enabling manufacturing of a thin semiconductor device. For a laminated structure of a semiconductor wafer and an encapsulation layer of resin, warpage of the semiconductor wafer is due to the difference in thermal expansion coefficient between the wafer and the encapsulation layer. Thus, once the semiconductor wafer is released from the device for maintaining the wafer flat, the semiconductor wafer tends to be warped excessively. [0009]Careful investigation of various conditions for grinding the back surface of a semiconductor wafer revealed the following facts. [0010](1) Warpage of a semiconductor wafer is enhanced if chipping (e.g., larger than 100 .mu.m) occurs at many locations on the circumference of the wafer. Poor surface roughness of the wafer due to the chipping impairs the resistance of the wafer to warpage, promoting further warpage. [0011](2) Warpage of a semiconductor wafer depends on the surface roughness of a wafer after grinding. High surface roughness impairs the resistance of the back surface of wafer to warpage, promoting warpage of the wafer. [0012](3) Warpage of a semiconductor wafer depends on the flexural modulus of an encapsulation layer at room temperature. There exists an optimum value of flexural modulus regardless of the thickness of a semiconductor substrate. SUMMARY OF THE INVENTION [0013]An object of the invention is to provide a method for minimizing the warpage of a semiconductor wafer during a grinding stage of the manufacturing process of a semiconductor device. [0014]Another object of the invention is to provide a semiconductor device having minimum warpage. [0015]A method is used for manufacturing a semiconductor device including a circuit-fabricated side on which an encapsulation layer is formed. [0016]The method includes the following steps: [0017]placing a semiconductor wafer on a suction surface of a suction stage, the suction surface having a diameter in the range of 99 to 100.5% of a diameter of the semiconductor wafer; [0018]holding the semiconductor wafer on the suction surface of the suction stage by suction; and [0019]grinding a back surface of the semiconductor wafer. [0020]The grinding is performed such that a surface roughness of the ground back surface is not greater than 5 nm. [0021]The method further includes forming the encapsulation layer having a flexural modulus not smaller than 12 Gpa and not larger than 18 Gpa. [0022]Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Continue reading... Full patent description for Semiconductor device and method for manufacturing the semiconductor device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Semiconductor device and method for manufacturing the semiconductor device 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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