A Study On Highly Oriented AlN Thin Film Prepared By Pulsed Laser Deposition

AlN is aⅢ-Ⅴnitride semiconductor material with excellent properties and wide band-gap, especially, highly oriented AlN thin film, which has many advantages in chemical stability, thermal conductivity, high acoustic transmission, high mechanical strength, electrical resistance, optical and electrical properties et al. Therefore, it has broad application prospects in microelectronic devices, optoelectronic components and SAW devices. At the same time, pulsed laser deposition (PLD) is an advanced technology of preparation of high quality thin film. We have chosen pulsed laser deposition under different conditions to study the optimum process parameters of preparing high oriented AlN thin films.AlN thin film preparation methods are mainly physical vapor and chemical vapor deposition. In the paper, we have described the basic theory, advantages and research developments of various thin film deposition, then, the latest research issues, research status and application prospects we have introduced. With the basic principles, preparation process and technical characteristics of pulsed laser deposition, we have designed the concrete steps, the essentials of implement and cautions. In the use of pulsed laser deposition we have prepared several groups of AlN thin film samples, by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscope (AFM) we have analyzed the orientation and structure of the samples. Then, we have discussed the effect of various deposition conditions to the quality of the AlN thin film. Finally, we have gotten the following results.Firstly, it is the discipline of process parameters to the film crystalline orientation. Within a certain range, the larger laser energy density, ambient pressure and substrate temperature are conducive to the crystallization of AlN thin films. In the lower laser energy density (0.60J/cm~2~ 0.77J/cm~2), higher ambient pressure (10Pa~100Pa) and lower substrate temperature (RT~200℃) AlN thin films is inclined to be the (100) preferential growth. In the lower higher energy density (1.17J/cm~2~ 1.60J/cm~2), lower ambient pressure (0Pa ~ 5Pa) and higher substrate temperature (500~800℃) AlN thin films is inclined to be the (002) preferential growth.Secondly, it is the effect of process parameters to the film deposition rate. While the laser energy is greater than the threshold, with the energy raising the deposition rate has increased. And the higher temperature would have increased the film growth rate.Thirdly, it is the effect of process parameters to crystal size and surface morphology of thin film. Raising the laser energy density, environmental pressure and substrate temperature increasing the crystal size and film surface roughness.Finally, we have succeed in preparing (002) orientation and good quality AlN thin film with the laser energy density (1.17J/cm~2), environmental pressure (5Pa) and substrate temperature (500℃).