The Cu-induced solid phase crystallization of undoped a-Si thin films deposited by low pressure chemical vapor deposition (LPCVD) has been investigated. In this study, we used Cu-solution coating method by spin coater. The Cu-solution coated a-Si films were then thermally annealed at relatively low temperatures, typically in the range of 530~600℃. The crystallinity of polycrystalline films was investigated by XRD, Raman spectroscopy and the morphology and microstructures were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) as a function of Cu concentration of solution, annealing temperature and time. From XRD and Raman scattering analysis, the thermodynamic parameters for the amorphous and crystalline phases were extracted. The electrical resistivities of the crystallized films were measured by four-point probe method and the final grain size was estimated from TEM dark field images. We observed dendritically growing fractals during heat treatment. The fractal size was related to the Cu concentration of solution. At the early stage of crystallization, the fractal center-to-center distance decreased as the Cu concentration of solution increased. In addition, final fractal size decreased due to impingement of neigboring fractals as the Cu concentration of solution increased. From this result, Cu appears to play an important role in crystallization of a-Si. The fractal growth of the dendrites indicated a growth process similar to one known as diffusion-limited aggregation (DLA). The diffusion of Si to the growing dendrite is the rate-limiting step of the crystallization. The incubation time and characteristic crystallization time were reduced as the Cu concentration of solution increased. As the annealing temperature increased, the incubation time and characteristic crystallization time were drastically reduced, small increase in grain size and decrease in electrical resistivity were observed. The final grain size was 0.3~0.4㎛ and the activation energies of grain growth calculated from Arrehnius plot for 10 ppm and 1000 ppm Cu-solution coated Si films were 2.67eV, 2.89eV, respectively.
