Crystallization of Hydrogenated Amorphous Silicon Thin Films Using Combined Continuous Wave Laser and Thermal Annealing

The thermal process of amorphous silicon thin film crystallization when combined with an aluminum (Al) film using a continuous wave (CW) laser is accompanied by additional interactions induced by the aluminum layer. This technique is frequently employed to optimize the crystallization process and enhance the quality of crystalline silicon by combining the thermodynamic effects of laser annealing with metal-induced crystallization (MIC). Hydrogenated amorphous silicon (a-Si:H) films were deposited using the plasma-enhanced chemical vapor deposition (PECVD) process on Corning glass substrates. An aluminum overcoat was deposited on the films. The specimens were irradiated with a continuous wave (CW) argon-ion (Ar +) laser beam of varying power density and duration. The samples were then annealed at 250 °C for 15 min to convert the amorphous silicon into polysilicon film. The grain size of the polycrystalline silicon films varies by varying the laser power density and the exposure time. The polysilicon grains acquired diameters ranging from 0.4 to 1.25 µm when the laser power density was set between 74.7 W/cm2 and 94.3 W/cm2. The grains with a size ranging between 1 and 2.5 µm showed plate-like and dendritic-like configurations when laser power densities changed between 31.4 and 74.7 W/cm2. The X-ray diffraction analysis (XRD) analysis revealed polycrystalline silicon with expected relative strengths.