Study On The Polishing Process And Annealing Treatment Of LiAlO₂

In this research, LiAlO₂ crystal was fabricated by Czochralski method in Berlin Institute of Crystal Growth, and then cut into small pieces with the direction of (100) crystal orientation. The effects of polish process parameters, such as polish grit, polish velocity, polish time and polish pressure on the morphology ofγ-LiAlO₂ was investigated. The surface morphology and arithmetical mean roughness of surface (Ra) after different process was investigated by optical micrometer, scanning electron microscope and atomic force microscopy. The result shows that the match employment of Al₂O₃ with SiO₂ turbid liquid is the prerequisite for the high quality substrate. The Ra reduces firstly and increases afterward with the increase of wheel velocity and polish pressure, while decrease with the polish time. Material removal rate (MRR) increases firstly and reduces afterward with the increase of wheel velocity and polish pressure. The optimum operation data are got by a set of selection of the technological parameters and the corresponding Ra was 2.695nm, which can be used for epitaxial growth of GaN. The mechanism of reaction between SiO₂ and LiAlO₂ during polish process was investigated carefully.The process of annealing treatment was performed to simulate the growth of GaN film. And the effect of annealing treatment, such as annealing temperature and the time of heat preservation on the morphology ofγ-LiAlO₂ was investigated. The result shows that with increasing the treat temperature,γ-LiAlO₂ will resolve and Li⁺ volatilize, decreasing the surface morphology. Appropriate preservation times can increase the crystal perfection, release the heat stress generated in the crystal growth. The characteristic and density of crystal dislocation before and after annealing was observed using chemistry etching method and the three dimensional morphology was obtained by Laser Scanning Confocal Microscope. The formation mechanism of defect during Czochralski process was presumed compared with its atomic structure.