Dynamic Simulation Of Growth Process Of Czochralski Silicon And Analysis Of Oxygen And Carbon Impurities

Silicon single crystal is the key material for fabricating micro and nano integrated circuit chips.Its quality has a direct impact on the performance of power devices.The Czochralski(CZ)method is currently the main method for growing crystals.The flow,heat transfer and mass transfer of the melt during crystal growth,especially the small fluctuations at the triple point and the impurity transport in the furnace directly affect the quality of the crystal.In order to improve the quality of large-size silicon crystals,it is necessary to establish a more approximate dynamic model by integrating various factors,and analyze the distribution characteristics of oxygen and carbon impurities in the furnace and and the etching evolution on graphite modules to better guide the actual CZ silicon single crystal production.The crystal growth process is essentially characterized by the coupling of magnetic field,thermal field,gas field and other physical fields,and the difficulty of mechanism modeling.In practice,it often relies on experience and has not yet formed a set of effective strategies.Numerical simulation based on finite volume method is an effective method to solve such problems.At present,the research on establishing a steady-state model in a two-dimensional environment is quite mature,however the stage with strong transient characteristics such as crowning growth,the dynamic factors of the crystal growth process can not be ignored,and the steady-state assumption can not meet the research requirements.In addition,the quality of silicon single crystal is also put forward higher requirements,in which the oxygen and carbon content is an important indicator of quality.Therefore,this paper has done the following research on the growth process of silicon single crystal by establishing a numerical model based on finite volume method:1.Quasi-steady and dynamic models are established to simulate the crystal growth process,and the results of the two models are compared.It is found that the quantitative difference of temperature is less than 3K in the body growth.The V/G ratio and thermal stress distribution show the same qualitative results.But for the crowning growth and cone growth,the temperature and thermal stress distribution in the crystal show the difference of dynamic and quasi-steady modeling results.Further,taking the crowning growth as an example,by calculating the change of crystal-melt interface shape at different times,it is found that the crystallization rate at the center of the interface is unstable,the fluctuation of interface position must be studied through dynamic modeling.Therefore,the dynamic modeling research is better for the strong dynamic phase with severe diameter changes.2.In view of the phenomenon of breakage and dislocation in the process of crowning growth,the crystal growth theory and numerical simulation are combined to explain the cause of formation,and the improved heater temperature compensation curve is obtained,which is verified by experiments,providing a reference for seeking the best technological conditions in the crystal growth experiment.3.In order to clarify the etching of the carbon and the deposition of silicide on the surface of the guide tube and the heater in the CZ-Si crystal growth,the oxygenation chemical model is first established to predict the occurrence of the deposition reaction,it is found that the simulation results of the guide tube and the heater are matched with the experimental measurements,and then the thermal zone structure of the CZ furnace is changed from the viewpoint of the chemical reaction temperature,and the argon gas flow rate and the furnace pressure are changed to study the chemical reaction of the surface of the guide tube and the heater.The change leads to the following conclusions:(1)After optimizing the structure of the furnace,it was found that the deposition sites of silicon and silicide(here mainly SiO2)on the guide tube were transferred,the deposition rate was significantly reduced,but the chemical reaction area was increased,and new carbon etching and silicon deposition have occurred at the top cover.New silicide deposits and carbon etches appear on the heater surface,and the deposition area is large,which greatly depletes the life of the heater.(2)Increasing the pressure in the furnace,the silicide deposition rate is rapidly reduced,and at the same time,the etching rate of carbon is also decreasing,which fundamentally suppresses the consumption of carbon and reduces the carbon contamination in the crystal.(3)After optimizing the thermal insulation structure,the CO and SiO concentrations in the gas decrease with the increase of the argon flow rate,and the increase of the gas flow rate effectively suppresses the generation and reverse diffusion of CO.Through the above research on the crystal growth process,it provides a reference for the future thermal field design of CZ-Si crystal growth process,and lays a foundation for further research on crystal growth oxygen and carbon impurities and sediment evolution.