Study On The Distribution Of Temperature Field In Large Size SiC Single Crystal Growth Furnace

As an important member of the third generation semiconductor material,SiC crystal has excellent physical and electrical properties,and it's suitable for high frequency,high power,radiation resistance,corrosion resistance and high temperature applications.For the growth of SiC crystal,The PVT method now is the most widely used growth technique.Because the growth of SiC crystal is in a fully enclosed crucible growth chamber,in which the temperature is more than 2000? and at this high temperature,it is impossible to observe the growth process directly.By using the traditional method of "trial and error"to find the crystal growth rule and accumulate the experience of crystal growth,it is obvious that the experimental amount will be huge,and also the experiment time will be too long and the cost will be too much.Therefore,the establishment of corresponding SiC crystal growth model and the application of modern numerical simulation technology to carry out numerical experiments,can be used to guide the growth of SiC crystal by PVT method,and it has become an indispensable technology.For the growth of SiC crystal using PVT method,the temperature and temperature gradient are the two most considerable parameters,which directly determines the density and transport direction of gaseous components decomposed and sublimated by SiC and also affect the growth morphology and growth rate of crystal.Therefore,the distribution of the temperature field affects the quality of the SiC crystal.In this paper,the characteristics,application fields and growth methods of SiC crystal are briefly introduced,and so as its development and research status.Then we give the relevant theoretical knowledge about temperature field distribution in a SiC crystal growth furnace.The research work and results can be summarized as follows:1.The finite element analysis software was used to rmodel the half cut surface of the 6 inch SiC crystal growth furnace,and the geometric model was discretized into a finite element model,and the appropriate boundary condition was set.2.The influence of the current on the heat distribution and heat production rate of the system was studied.It was found that increasing the current intensity can increase the heat generation rate without affecting the relative heat generation distribution of each part of the equipment,while increasing the current frequency will both increase the heat generation rate and the relative heat production distribution.In addition,it is necessary to take into consideration that the increased energy waste due to the increase of the heat generation rate of the insulation material.3.The temperature rise process of the growth furnace in the constant current heating mode was simulated and analyzed.It was found that a constant 180A and 10kHz current is suitable for the device,and the temperature field.The simulation gives the growth temperature curve of each part of the growth furnace.At the same time,the axial temperature gradient and the radial temperature gradient of the growth furnace are obtained,which is 7?/cm and 2?/cm respectively,meeting the expectation.4.The influence on the distribution of the temperature field by the relative position of the coil and the graphite crucible was studied.It was found that the change of the coil position affects the distribution of the temperature field in the growth chamber,but has no effect on the highest temperature that the growth chamber can reach.The relationship curve between the relative position of the coil and the graphite crucible and the distribution of the temperature field was given.5.A high-reliability control system for controlling the induction coil lifting was designed.The system can run according to the user's set operating speed and distance to precisely control the coil's lifting.At the same time,a UI interface was designed to interactively display the current lifting state.Through the photoelectric coupling isolation and the limit detection circuit design,the reliability of the system operation can be ensure.Tests show that the control system can exhibit good real-time performance and stability,with small running errors and meet the control needs.