Study On Temperature Field And Intelligent Control For Aluminum Nitride Crystal Growth System

Aluminum nitride(Al N),as one of 3rd-generation semiconductor's representative,has direct and ultra-wide gap(6.2 e V)and performances well in high melting point,high breakdown field strength,high electron saturated mobility,high anti-radiation,etc.It's suitable for producing deep-UV devices,thermostability devices,high power devices,high frequency devices,radioresistance devices,and so on.At the same time,due to the similar coefficient of thermal expansion and little lattice mismatch compared to other Group ? nitrides(e.g.,Ga N),Al N is the best buffer layer material for the epitaxial growth of them.However,it's hard to gain single crystal with large size or high quality at present,because the lack of appropriate substrate,unstable and faulty growth technique and other reasons.In this paper,fundamental work has been done to get large size and high quality crystal,containing the preparation of Al N by Physical Vapor Transport(PVT)in tungsten substrate,optimizing the growth equipment structure to get the most suitable thermal field,and designing excusive temperature control system for growth.First,through the present situation of Al N growth at home and aboard,and combining our experiment experience,the prime reasons of the limits of size and quality are analyzed.Then the ideal processing conditions and actual methods for the preparation of Al N crystal growth by PVT are proposed.Secondly,the advantages and disadvantages of medium frequency induction heating and resistance heating used in Al N crystal growth by PVT are contrasted.It's found that resistance heating can provide more fitted thermal field in growth.And then,the experiment scheme of thermal field inversion is proposed.For this purpose,the chamber structure with double-heating and different sharps of heaters are designed.The resistance values of each heaters are calculated.The thermal field of the structure and the effects of these heaters are simulated by finite element analysis software.The best coordination of two kinds of heaters and the suitable number of insulation layers are selected.Finally,for the growth chamber structure above-mentioned,a suit of temperature control system,special designed for the experiment scheme of thermal field inversion,is projected to achieve the preparation of Al N with large size.To actualize automation in the processing of growth and match the requirement of thermal field inversion,PLC is chosen as main tool,thermoelectric couple,infrared thermometer,temperature controller and others are chosen as auxiliary tools in this system.In the end,the system was applied to actual experiment researching.The system has good effect in the preparation of Al N crystal growth by the characterized data from the samples we got.