Miniaturization and slimness of electric and electronic devices require the thinning of dies. During the manufacturing of a semiconductor chip such as an integrated circuit, a circuit may be formed on a semiconductor wafer and then, the wafer may be individualized and separated into respective portions or dies, whereby costs may be reduced and a processing process may be simplified, as compared to the case of forming individual devices.
FIG. 1 is views illustrating a process of separating dies from a wafer in the related art.
Referring to FIG. 1, in order to protect a circuit 2 formed on one surface of a wafer 1, a protective film 5 may be attached onto the wafer 1 on which the circuit 2 is formed (refer to FIG. 1(a)). Back grinding may be typically performed on the wafer 1 before being separated into dies 3 through chemical or mechanical planarization or using other technologies for removing a material, and in this case, the material may be removed from a lower portion or the back side of the wafer, such that the wafer has a smooth lower surface. Such a process is called “wafer back grinding”, that is, a process of supporting the wafer 1 using a wafer chuck 15 prior to the assembling of a semiconductor, and thinning the wafer 1 by a grinder 10 to uniformalize a thickness of the wafer 1, simultaneously with grinding the wafer to a desired thickness (refer to FIG. 1(b)). In addition, a protective film 5 may be removed and in order to mechanically support the dies during a separation process, a mount film 20 may be attached and fixed by a wafer ring 25 (refer to FIG. 1(c)). By the mechanical forming of a scribing line 30 through the wafer 1 from an upper surface of the wafer 1, cut individual dies 2 physically separated from the wafer 1 may be provided (refer to FIG. 1(d)). In order to detach the individual dies 2 from the wafer 1, the wafer ring 25 may be moved to expand the mount film 20 (refer to FIG. 1(e)). In addition, the individual dies 2 may be completely separated from the wafer 1 (refer to FIG. 1(f)), and the separated dies 3 may be detached from each other to be assembled in an integrated circuit chip, or be directly fixed to a printed circuit board (PCB). The electrical connection of the separated dies 3 may be performed by one or more electrically-conducting bonding wires disposed on the dies. In particular, the process of separating the dies 3 from the wafer 1 is called a sawing or dicing process.
FIG. 2 is a view illustrating wafer back grinding in the related art. FIG. 3 is a view illustrating thickness variations of the wafer according to the wafer back grinding in the related art.
Referring to FIG. 2 and FIG. 3, a wafer grinding technique using a grinding wheel 10 according to the related art is a method of grinding directly a surface of the wafer 1 by the grinding wheel 10 rotating at high speed, and is conducted while spraying DI water during a process in order to remove mechanical fractional heat and foreign materials. The wafer 1 disposed on the wafer chuck 15 may be unavoidably, mechanically stressed. The stress may cause, after grinding, breakage of the wafer 1 or the like, in a process of detaching the protective film 5 attached to an opposite surface. The surface of the wafer 1 on which the circuit 2 is formed may be fixed to the wafer chuck 15 in a state in which the protective film 5 is attached to the wafer 1. The protective film 5 may bent according to a pattern height of the circuit 2 of the wafer 1 and in this state, may be fixed to the wafer chuck 15. A shape of a pattern surface transferred onto the protective film 5 of the wafer 1 may be shown on a ground surface of the wafer as the wafer 1 is fixed to the wafer chuck 15 and is ground to have a reduced thickness, thereby causing variations in the overall thickness of the wafer 1.
In addition, an etching method of chemically grinding the back side of a wafer is a method of reducing a thickness of the wafer by melting a surface of the wafer with the use of strong chemicals. Such a method is a removal method using a chemical reaction between the chemicals and a material of the wafer and requires a relatively long process time, as compared to mechanical methods.
Both the mechanical method and the chemical method as described above may have defects in which a wafer may be mechanically or chemically stressed during a wafer thinning process of thinning the wafer, thereby causing cracks or the like in the wafer after the thinning. In addition, during the wafer thinning process of thinning the wafer, a considerable amount of waste water may be caused and accordingly, a separate processing cost may be required. Further, the both methods may have common defects in which a considerable thickness of the wafer is unable to be recycled and is discarded.