Simulation And Design On MOCVD Reactor By Induction Heating

As MOCVD (Metal Organic Chemical Vapor Deposition) equipment is the method of research and production of the compound semiconductor materials, especially in the aspect of industrial production, its high quality, stability, repeatability and large scale can not be replaced by other equipments used to grow semiconductor materials. However, the reactor chamber is the core part of the MOCVD equipment, whether the design of the reactor is better or not is directly related to the film quality grown by the MOCVD. Now, it is an indispensable method to model and simulate the reactor by using the computer. In this paper, the vertical MOCVD reactor chamber heated by induction is simulated and analyzed, aimed at researching the heat and flow fields in the reactor, deeply and systematically.Firstly, mathematic model of the MOCVD reactor chamber by induction heating is built, with the corresponding parameters of the model presented and the process of the simulation given. Based on these, a research on the magnetic field in the reactor is done. Furthermore, the effects of the coil turns, the applied current intensity, the current frequency and the distance between coils on the magnetic field and the distribution of the joule heat are analyzed, respectively.The relations of the temperatures of the susceptor and substrate changed with the applied parameters are studied. The results show that the distributions of the temperature in the substrate and susceptor have an obvious skin effect. And the temperatures in the substrate and susceptor are inversely proportional to the convective heat transfer coefficient, but its effect on the temperature distributions is less. In addition, the temperature distributions in the substrate and susceptor are proportional to the current frequency, the current intensity and the coli turns, respectively, however, the uniformity of the temperature distribution in the substrate is inversely proportional to them. It can be seen that the temperature in the substrate decreases with increasing the distance between coils, but the uniformity of the temperature distribution in the substrate is improved. It can be found that the heating efficiency gets the highest under the conditions that the coils distribute symmetrically with respect to the middle section of the susceptor, and that the distance between coils is less, as well as the radius of the coils. The relations between the size of thermal hole and the temperature distributions of the substrate and susceptor are analyzed. The results show that the influence of the size of thermal hole on the temperature distributions of the substrate and susceptor is less, but it has strong effect on the temperature of the top point of the thermal hole. By optimizing the size of the thermal hole, the size of the thermal hole which makes the absolute value of the difference between the temperature of the top point of the thermal hole and the average temperature of the substrate reach the minimum values is obtained.The conventional susceptor is improved by using a ring groove around the conventional susceptor, which solves the problem of the nonuniform temperature distribution of the substrate under the conditions of induction heating. Furhtermore, the heat transfer mechanism of the heat in the susceptor with the groove is discovered, by analyzing the temperature distributions in the susceptor under different heating time. That is, the groove changes the directions of heat conduction and the distributions in the susceptor. It is also found that the location and size of the groove have a strong influence on the temperature uniformity of the substrate, as well as the height of the susceptor. And the heating structure which makes the temperature in the substrate uniform can be obtained. The optimized structures for heating the substrates of 2 inches to 6 inches are also presented. In addition, the GaN films with the diameter of 3 and 4 inches are successfully grown, by using the optimized susceptors to heat the 3-inch and 4-inch substrates, respectively, which shows the feasibility of the heating structure.However, with increasing the size of the substrate, the thickness of the optimized susceptor increases by using this method, which may bring about a certain difficulty in quickly switching temperature in the substrate. Therefore, we further improve and optimize the heating structure for the large-size substrate (such as the 6 inches, 8 inches and 12 inches). Thereby, we solve the problem of designing the heating structure for large-size substrate. The simulated results show that the uniformity of the temperature distribution in the substrate under the conditions of coils under the susceptor is better than that of coils outside the reactor, but the heating efficiency is lower than the latter.The mathematic model for the flow field in the reactor is built in this paper. Based on the experiment results, the flow field in the reactor is simulated. The simulated results are in agreement with the experiment results. It is found that the distributions of the flow field in the reactor is related to the wall temperature, the pressure of the reactor and the size of the inlet, by analyzing the flow field in the reactor used to grow one single and two-inch wafer. Lower wall temperature, larger inlet and lower pressure can reduce the vortex flow in the reactor, which can improve the quality of the film growth. By analyzing the flow fields in the reactor with the conventional susceptor and with the optimized susceptor with the groove, we find that whether the susceptor with or without groove has little influence on the flow field.