Abstract
It is difficult to fabricate a nonwarped substrate, because a thin wafer cannot be fixed during the polishing process without deformation occuring. To resolve this matter, a SiC freezing pin chuck has been developed. This paper describes the peeling strength of freezing liquid due to the thermal stress generated by polishing and the deformation of a large warpage quartz wafer fixed by the freezing pin chuck. Stress distributions in the frozen liquid caused by the thermal stress were calculated with the finite element method (FEM). When the quartz glass wafer is fixed with the freezing liquid cooled at 5℃ and the surface of the wafer is heated at 30℃, the maximum tensile and shear stresses become 1700 and 1100 kPa, respectively. These are smaller than the experimental results, 1800 and 1200kPa. Accordingly, it is inferred that the wafer is not peeled from the chuck. For the 300-mm-diameter, 1.2-mm-thick quartz glass wafer with the warpage of about 200 μm, the deformation amount between initial and before solidifying with the freezing pin chuck is decreased one tenth less than that with the plane freezing chuck, and that between before and after solidifying becomes one half less than that with the other. As a result, it was clarified that three times polishing with the freezing pin chuck enable to decrease the warpage of about 200μm to less than ±1μm.
