dc.description.abstract | GaN is a remarkable semiconductor material in the current investigation. Because of the unique advantages of high purity, good quality, and suitable method for high mass production with a large deposition area, the films are produced by MOCVD. At present, MOCVD technique has been widely applied to manufacture GaN films.
This study uses the FEM method, builds the mechanism of chemical adsorption based on the Langmuir isotherm. After comparing the adsorption rate of the different species, MMG is entered into the major consideration, as the result, the MMG molecule which deposited on the wafer surface is mostly generated by 3 gas reaction processes.
Firstly, the study modifies the temperature variation from 550 to1050℃,makes the comparison with the experimental results, and investigates the effect of varying these manufacturing parameters, such as gas flow rate (25-75 slpm) , rotation rate of wafer carrier (500-1800 rpm), and chamber pressure (30-90 Torr), on the growth rate and film thickness uniformity.
The results indicate that the increase of gas flow rate improves the growth rate of the film but makes deterioration of uniformity. Moreover, enhancing the chamber pressure and wafer carrier rotation rate can accelerate the diffusion speed of specie to get a better growth rate and film thickness uniformity. However, higher speed and higher pressure lead to the instability in the flow field.
After that, we considers the real gas inlets of the 3D model of Veeco D180 chamber, design of the basic geometry and then the study of optimization of the gas inlets was done. The result presents that when the radius is 177mm, ratio of h/D is 0.51, the film thickness uniformity is better. The setting of the hydrogen inlet can effectively improve the species aggregation below the viewport, and the vertical below the viewport will disappear when vH2:vTMG =4.
Finally, the study of optimization of the gas inlets was done. The results shows the inlet design with circle arrangement will enhance the diffusion of gas and also reduce the uniformity of the film. | en_US |