The Study On Preparation Of Large Area Bi_3.15Nd_0.85Ti₃O₁₂ Thin Films By Pulsed Laser Deposition

The technology for preparing the large area ferroelectric films has attracted intensive interest for the applications of ferroelectric films in integrated circuits and integrated ferroelectric devices. In this dissertation, we develop a new pulsed laser deposition technology to prepare 5 inch Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) thin films utilizing the laser beam scanning over the large diameter targets. The main research contents and the obtained results are summarized as follows:1. We construct a large area thin films growth model for pulsed laser deposition to simulate the deposition tracks of the plasma plume on the substrate. The kinetics growth process of BNT thin film is described by the growth model. Then, the deposition tracks of the plume are calculated and simulated by the MATLAB software, and the theoretical value of appropriate deposition radius is gotten to grow the large area thin film uniformly.2. We get the appropriate growth parameters for growing uniform 5-inch large area BNT thin films by comparatively analyzing the results between the thin films growth model mentioned above and experimental deposition. The optimal deposition radius is obtained by the deposition experiment with the stationary laser beam. Different plume deposition tracks are simulated by chancing the scan speed of the laser beam and the deposition time. Moreover, the 5-inch BNT thin films are prepared with different deposition tracks and deposition radius. The relationship between deposition tracks and film thickness distribution on the Si wafer is discussed by analyzing the thickness uniformity of the 5-inch BNT thin films. Uniform thin films of BNT have been deposited on 5-inch Si wafer and the maximum variation in film thickness is found to be less than±2.5%.3. We characterize the microstructures, optical parameters and electrical properties of the prepared thin films by an x-ray diffractometer, scanning electron microscope, automated thin-film thickness mapping system, ferroelectric analyzer and semiconductor parameter analyzer respectively. The influence of growth conditions on the film orientation and crystallinity are studied systematically. The refractive index, extinction coefficients, ferroelectric properties and leakage current of the prepared thin films are studied systematically.