Numerical Analysis And Optimization Of Thermal Field In High-temperature And Large-sized MOCVD Reactor

The ?-nitride semiconductor thin film material is the basis for the preparation of high-brightness S-photodiodes,semiconductor lasers,ultraviolet detectors,and high-frequency,high-power microelectronic devices,and is considered to be the most important third-generation semiconductor material after silicon.Metal-organic Chemical Vapor Deposition(MOCVD)is one of the important technologies for the preparation of nitride semiconductor materials.Due to the complexity of MOCVD technology,the film is affected by many factors during the growth process,and the uniformity of substrate temperature distribution is an important factor affecting the growth of the film.With the widespread use of nitride thin film crystals,the market has also placed new demands on large-sized crystal growth.At present,the research on the growth field of nitride growth below 8 inches is mature at home and abroad,but the research on the thermal field of MOCVD reaction chamber with large size(above 12 inches)is less.The MOCVD heating system is generally heated by electrical resistance and electromagnetic heating.Regardless of the heating method,there is a problem that the substrate temperature uniformity is low.The purpose of this paper is to establish a two-dimensional model of the reaction chamber by means of simulation software,simulate the environment of nitride growth,and observe the influence of various related parameters on the thermal field of the reaction chamber and optimize it to improve the temperature uniformity of the substrate.The ultimate goal.In this paper,a large number of simulation calculations are carried out according to the characteristics of the two heating methods.The main contents are as follows:(1)In the conventional resistive heating system,part of the heat generated by the resistance heating is carried away by the gas in the heating chamber and the radiation is lost,resulting in a decrease in the efficiency of the resistance heating.In particular,when heating a large-sized substrate sheet,the problems of heating efficiency and temperature uniformity are more prominent.In order to solve the problem of low heating efficiency of the resistance heating system,heat insulation panels are added in the heating system of the reaction chamberto improve the heating efficiency of the heating system,and the factors such as the height,the number of layers and the length of the heat insulation board are analyzed.The influence of uniformity of substrate temperature distribution is proposed.A new pedestal structure is proposed.The heating resistor is placed inside the pedestal to adjust the direction and rate of heat transfer,so that the temperature tends to be uniform when heat is transferred to the substrate..(2)In the traditional electromagnetic heating system,the heat generated by the heating system is directly supplied to the susceptor,and the heating efficiency is high;however,due to the skin effect of the current,the substrate temperature distribution is not uniform,especially when growing a large-sized thin film crystal.The effect is more prominent.According to the heating characteristics of the electromagnetic heating system,the focus of this part of the research is to improve the temperature uniformity of the substrate: study and analyze the influence of electrical parameters on the thermal field of the reaction chamber;a new pedestal structure is proposed: silicon carbide and graphite are selected as the new base.The material of the seat embeds the graphite ring into the interior of the silicon carbide,and utilizes the difference in thermal conductivity between the silicon carbide and the graphite to change the heat generation and heat transfer at various positions in the susceptor,thereby improving the uniformity of the substrate temperature distribution.(3)In the MOCVD reaction chamber,the reaction gas inlet enters,a crystal film is formed above the substrate,and the excess gas is discharged along the outlet,so the flow field has a great influence on the growth of the film.For the thermal field in the reaction chamber,the influence of the flow field on the thermal field is mainly reflected in the inlet flow rate of the reaction gas.Therefore,different sizes of gas flow are injected into the reaction chamber inlets of the two heating modes,and the gas flow rate is observed.Effect on substrate temperature.The results show that the flow rate of the reaction gas has little effect on the thermal field,the gas flow rate increases,and the temperature decreases.The gas flow has little effect on the temperature uniformity distribution of the substrate.