The Influence of Sputtering Power of Aluminum Film in Aluminum Induced Crystallization of Low Temperature Poly-Silicon Film

This study produces low-temperature poly-silicon (LTPS) film by aluminum induced crystallization (AIC) method on Corning Eagle2000 glass substrate. Through the control of different sputtering power in depositing aluminum film, five kinds of specimens with sputtering power of 100, 200, 400, 800 and 1600 Watts, respectively, are made. Crystal quality, surface morphology, roughness and film residual stress varying with aluminum film sputtering power are analyzed with XRD, Raman spectra, SEM, AFM and alpha-stepper. Results show that surface roughness increases proportional to sputtering power. More and more bulges and cracks are observed on the poly-Si thin film in SEM micrographs as the sputtering power increases. A broken poly-Si film is observed in SEM micrograph when Al sputtering power is 1600 Watts. The film stresses calculated are tensile when sputtering power are 100 and 200 W from the measurement results of alpha-stepper both before and after annealing process. However, if the sputtering power is further increased to 400 and 800 Watts, the film stresses will become compressive. This explained the reason why bulges and cracks increase with the sputtering power. The film stress cannot be calculated correctly because the film has already broken and the equation for calculating stress is no more applicable. Therefore, from the viewpoint of minimal film stress, a sputtering power of aluminum film of 200 to 400 Watts will be the optimal range in our study