The Design And Experimental Study On Vertical Furnace Of LPCVD

LPCVD is one kind of the key process equipment for the manufacturing industry of semiconductor integrated circuit.This LPCVD equipment is mainly used for thin film deposition process of Poly silicon(Poly-Si),Silicon nitride(Si-Nitride)in integrated circuit manufacturing,with high performance in equipment automation and process reliability.The success of the project broke the monopoly of foreign technology,made up for the lack of domestic technology,and was of great significance to the development of the semi-conductor integrated circuit manufacturing equipment industry in China.It can be applied to common process such as Poly-Si.We tried our best to successfully study core technologies such as thermal treatment system(heater),ULPA(Ultra Low Penetration Air Filter)systems,Load lock system(02 control),Wafer transfer system(boat elevator and manipulator),Vacuum control system,etc.This project has made a breakthrough in some key core technologies.These core technologies were practically applied to the equipment.The reaction chamber is the key component of semiconductor diffusion equipment.It is found that the deformation of silicon wafer on the three column boat is small in the design process.The thermocouple fixing device in the chamber of the reaction chamber is characterized by high reliability,simple structure,small space occupation and convenient installation on the premise of accurate positioning and firm fixation of the thermocouple.By calculating the heat of heat preservation barrel,the heat of silicon wafer,and the heat of quartz boat and reaction chamber in the process of falling boat,the total heat release in the process of falling boat is obtained,which provides the theoretical data for the design of microenvironment.In order to ensure the excellent performance of the equipment,two methods of heat exhaust and heat exchange are used to cool the microenvironment.The design of micro-environment heat discharge is realized by calculating the heat of exhaust system,air circulation system and heat exchanger.Through the simulation analysis of temperature field and airflow field,it can be seen that the velocity of the silicon wafer on the longitudinal section is not obvious,and the uniformity between the surfaces is better.The process tube each height velocity basically assumes the concentric circle state.A uniform spiral distribution of velocity streamlines was observed.The in-plane thin film is a little thinner than the inner one,and the bottom temperature of the reaction chamber is combined with the heating wire and the heat preservation barrel to cause the outer thickness of the thin film on the bottom of the reaction chamber to be thin.The results of gas and fluid simulation show that the thickness uniformity of silicon film is the best in the middle of the chamber and the uniformity between the two ends is worse.The bottom is influenced by pressure difference,and the top by velocity difference.For a single wafer,the pressure at the edge is greater than that at the center,and the fluid velocity at the edge is larger than that at the center.In the temperature uniformity test,it is found that increasing the gap between the inserts,reducing the distance between the top heat preservation barrel and the boat,reducing the OD248 SiC inserts,increasing the number of OD248 Si02 inserts,appropriately increasing the diameter of the insulation plates,and improving the temperature uniformity in the bottom plane.The functional verification of the corresponding system shows that the oxygen content in the microenvironment decreases to 5 ppm after 30 minutes of operation,which meets the design requirements.The test results show that the furnace body cooling rate can meet the requirements.The vacuum system has a bottom pumping rate of 5 m Torr and a leakage rate of 0.6 mTorr/min,which meets the requirements of the reaction chamber for the low pressure chemical vapor deposition process.The main performance indexes of the whole machine are obtained:film thickness uniformity,particle increment,metal element content,all of which meet the requirements of the process index,which shows that the LPCVD vertical furnace equipment has good process performance and stability.