Surface evolution and stability transition of silicon wafer subjected to nano-diamond grinding

In order to obtain excellent physical properties and ultrathin devices, thinning technique plays an important role in semiconductor industry with the rapid development of wearable electronic devices. This study presents a physical nano-diamond grinding technique without any chemistry to obtain ultrathin silicon substrate. The nano-diamond with spherical shape repeats nano-cutting and penetrating surface to physically etch silicon wafer during grinding process. Nano-diamond grinding induces an ultrathin “amorphous layer” on silicon wafer and thus the mismatch strain between the amorphous layer and substrate leads to stability transition from the spherical to non-spherical deformation of the wafer. Theoretical model is proposed to predict and analyze the deformation of amorphous layer/silicon substrate system. Furthermore, the deformation bifurcation behavior of amorphous layer/silicon substrate system is analyzed. As the mismatch strain increases or thickness decreases, the amorphous layer/silicon substrate system may transit to non-spherical deformation, which is consistent to the experimental results. The amorphous layer stresses are also obtained to predict the damage of silicon wafer.