| The emergence of MBE(molecular beam epitaxy)technology has greatly promoted the advancement of semiconductor film technology.The evaporation sources are mainly used to produce atoms or molecular beams,Which is the foundation and core of the MBE system.It is also the "bottleneck" product that domestic MBE companies can not break into the high-end market.As a derivative product of evaporation source,pyrolysis source is mainly used to evaporate and decompose the solid IV/V group substances which have high saturated vapor pressure and are easy to form clusters.Antimony-containing III-V semiconductor compounds are widely used in the fields of semiconductor lighting,fiber-optic communication and semi-conductor laser due to their high carrier mobility and ultra-narrow bandgap nature.Therefore,it is of great scientific research and application value to develop a cracking source that can vaporize and decompose antimony.In order to solve cracking source’s these questions that the overall structure is complex,the capacity is too large,the temperature of cracking zone is too low,and don’t can satisfy the local coating.A new type of high temperature cracking source equipment is designed,which includes evaporation device,cracking device,valve mechanism and cooling device.The steady-state thermal simulation of the heating area was carried out,and the temperature control experiment and analysis of the cracking source under different working conditions were carried out,and the actual coating experiment of the cracking source was analyzed.The main research content and results are as follows:1)The advantages and disadvantages of cracking source structure at home and abroad were analyzed,and a design scheme of high vacuum,small capacity,integrated structure and high temperature thermal evaporation cracking source with valve suitable for MBE technology was proposed,and the overall research scheme of the new high temperature cracking source was defined.2)The principles of source material evaporation,cracking and molecular or atomic coating were studied and analyzed respectively.The exact temperature of the cracking source was discussed.The design principle and scheme of the cracking source structure were given.The parameters and characteristics of the materials needed by the cracking source were analyzed.3)The cracking source structure is designed,the structure is highly integrated,the source material is convenient to replace,and the structure capable of realizing evaporation and cracking coating of the small-capacity source material is completed.4)Using the Workbench module of ANSYS simulation software,the steady-state thermal simulation of the cracking source structure was carried out under the conditions of with or without heat shield,preheating and coating.The simulation results show that the heat shield of the cracking source can provide better insulation effect for the heating area,the cooling water cover can provide good cooling effect,and the preheating and coating of the cracking source meet the structural design requirement.5)A vacuum experimental device is designed and built,and a nonlinear tuning PID controller based on genetic algorithm(GA)is designed;The results show that the actual preheating temperature of the cracking source is consistent with the simulation results,the overall coating temperature is stable,the overshoot value is less than 0.15℃,the steady-state error is less than 0.1℃,and the cracking source has a good temperature control effect.The temperature control response time of PID controller based on GA nonlinear tuning is close to the half of the constant voltage step temperature response time,which improves the heating efficiency of the cracking source.The coating experiment of the cracking source is carried out,and the experimental results show that the cracking source can achieve the requirements of precision coating. |
