Design And Implementation Of The Large-size Vertical HVPE Equipment Control System

As a mature semiconductor material,gallium nitride(GaN)is extensively used in power and radio frequency fields due to its excellent performance.Hydride vapor phase epitaxy(HVPE)method is the preferred way to provide GaN material in commercial because of its simple technology and mature application.At present,the domestic preparation of GaN substrate is still mainly 2-4 inches by HVPE method,and there are problems of low control accuracy,poor system stability and low automation in the process of growing GaN substrate,so the development of HVPE equipment control system that can grow higher quality and larger size GaN substrate has great application value.Therefore,based on national key research and development program,this thesis takes vertical HVPE equipment as the research object,designs and implements a HVPE equipment control system suitable for the growth of large-size GaN substrate.The primary study contents contain:(1)Considering the actual control demands of HVPE system,the general framework of HVPE equipment control system is constructed,the hardware and software structure of the system is divided,and the system workflow is projected.(2)Pointing at the problems of low control accuracy and poor anti-interference ability of HVPE equipment motion control,a HVPE motion control scheme using linear active disturbance rejection controller is planned,and the mechanical structure of lifting shaft and rotating shaft of the system is designed,the device selection and circuit design of the servo drive system are introduced in detail,the motor motion equation is given based on the principle of servo motor,linear active disturbance controller of the position loop and speed loop are designed to achieve accurate control of system position and speed.(3)Pointing at the problems of nonlinearity and strong coupling of HVPE equipment temperature control,a HVPE temperature control scheme using Smith-fuzzy PID controller is planned,the structure of furnace is improved and the hardware selection of temperature control system is introduced in detail,an approximate equivalent model of the furnace is established based on the thermodynamic principle,the fuzzy PID controller is constructed and used to the temperature control of the furnace,the Smith estimation algorithm is introduced to realize temperature lag compensation.(4)The prototype construction and configuration of the vertical HVPE equipment are realized,and the system process program and monitoring software is completed,and finally the overall test and growth proof of the prototype are conducted.As a result,the overall system performance is effectively improved,in which the average positioning error is reduced to 0.12mm,the relative error of speed tracking is reduced to less than 0.6%,and the mean temperature steady-state error is controlled within 0.213℃.Finally,the 6-inch high-quality GaN substrate material is successfully grown,reached the task index of the subject,and provided valuable design scheme and application case for the development and improvement of the existing large-size HVPE equipment and control system.