Study On Model Parameter Extraction And Total Ionization Dose Effect Modeling Of MOS Devices

In recent years,with the rapid development of space technology,such as aerospace,performance degradation and even functional failure of electronic components will occur under irradiation environment,which leads to higher and higher requirements for radiation resistance of electronic components.Among them,total ionization dose effect is the most obvious.The most basic component of the circuit,the metal oxide semiconductor field effect transistor(MOSFET),under the total irradiation dose,the important electrical parameters such as threshold voltage will change,which will cause great damage to the circuit system.Therefore,IC design engineers and researchers need to repeatedly carry out irradiation experiments,analysis and design when they develop high accuracy and high availability suitable devices or systems for irradiation environment.Because the cost of irradiation experiment is very high and time consuming is enormous,the establishment of numerical model of total ionization dose effect has become an important link in the research of irradiation effect and anti-irradiation reinforcement of electronic devices.This thesis proposes a new modeling method of the total ionization dose radiation effect of MOSFET,which combines the normal numerical model of MOSFET with the radiation leakage current numerical model.In this thesis,it is called "normal model and radiation current model".This method adds the total ionization dose current model to the normal numerical model of MOSFET in the form of external current source,which can make full use of the advantages of the normal model physical effect and the accuracy of the model.Compared with the traditional modeling method based on the physics,it can also save the analysis of the simple physical effects of the device and simplify the modeling process.Obviously,in this modeling method,the accuracy of the model is mainly determined by two parts : the accuracy of the normal model and the accuracy of the irradiated current model.Based on this core idea,this thesis mainly studies two main tasks: First,in order to get an accurate device normal model,this thesis proposes to use the Differential Evolution(DE)algorithm to extract the parameters of the normal model BSIM3V3.The traditional local optimization parameter extraction algorithm is complex and has many processes.In this thesis,DE algorithm is used to extract global optimization parameters.It can extract all the parameters at one time,and the time is short and the precision is high.In this thesis,the mutation process and crossover factor in the DE algorithm are set to adaptive factors that increase with the number of iterations.At the same time,in order to make the parameters extracted by the algorithm do not lose their true physical meaning,in the algorithm iteration process,each parameter is set up an evolutionary scope,in order to ensure the authenticity of the parameters.When extracting parameters from multiple data sets of different orders,this thesis proposes a fitness function that balances the weight of individuals according to the weight of data error,in order to balance the size of the error under different orders of magnitude.It is proved that the algorithm proposed in this thesis has faster convergence speed,higher accuracy and better performance than traditional local optimization algorithm and Particle Swarm Optimization(PSO)algorithm.Second,in order to establish the radiation current model of the device,a total ionization dose effect current model for MOSFET transistors with Shallow Trench Isolation(STI)region considering the device size and total ionization dose is established.With the development of technology and the progress of technology,the size of devices is also smaller.The gate oxide of devices becomes thinner and thinner.Therefore,to a certain extent,the leakage current of the devices decreases and the radiation resistance becomes stronger.However,the thickness of oxide layer is very thick in the STI region which separates many devices in the circuit.The leakage current in this part is the main source of leakage current in small size devices.In this thesis,a mathematical model is used to establish the total ionization dose radiation effect leakage current model in STI region.The size of the device and the total ionization dose are taken into account in the model.It is verified that the model can simulate the relationship between the leakage current and the total dose under different irradiation conditions.Finally,this thesis presents a method of modeling total ionization dose effects by combining the normal model parameters extraction by DE algorithm with the irradiated current model,and gives the specific process.