Molecular Dynamics Study on the Evolution of Hydrogen Ions, Crystal Defects and Stress in Single Crystal Silicon During the Annealing to Splitting Process of Smart-Cut?
Abstract：The ion implantation process and the annealing to splitting process in Smart-Cut? technology were simulated using molecular dynamics method. The splitting behavior at micro/nano-scale of hydrogen implanted single crystal silicon was investigated, as well as the evolution of distributions along the implantation direction of hydrogen atoms, silicon defects and average normal stress. Firstly, the variations of silicon crystal structure and forms of implanted hydrogen atoms and the splitting position were examined through OVITO and chemical bond analysis. Dividing the silicon crystal into elements of equal size and calculating the numbers of hydrogen atoms and silicon defects in each element, the distributions and distribution ranges of implanted hydrogen atoms and silicon defects were obtained. Splitting characteristics were then analyzed in terms of the evolution of distributions of hydrogen atoms and silicon defects. Meanwhile, variation of the distribution ranges with the annealing time was adopted to quantify the influence of hydrogen diffusion, thermal deformation and stress deformation. Finally, average normal stress was applied to feature the stress distribution. Research results show that silicon lattice structure in the hydrogen atoms concentration area is severely damaged by the atom implantation and the annealing.Various silicon-hydrogen compounds are formed via chemical reaction between hydrogen and silicon atoms and will transform their forms during the annealing to splitting process. Splitting generally occurs at the hydrogen concentration peak after the implantation process. Splitting of hydrogen implanted silicon experiences three stages: nucleation and growth of vacancy point defects without considerable local expansion of platelets, continuous growth of vacancy defects leading to remarkable local expansion of platelets, and Ostwald growth of platelets. Due to the influence of hydrogen diffusion and deformation, distributions of hydrogen atoms, crystal defects and stress exhibit different evolution characteristics for three stages with the progress of annealing to splitting process. Moreover, Numerical method established in this work to systematically and quantitatively analyse the wafer splitting in Smart-Cut? technology can be further applied to improve and optimize Smart-Cut? technology, and can also be potentially extended to ion irradiation and other related fields.
2023, Vol. 44 
