Study On Hot-carrier Effect In Ultra-deep Submicronmeter MOSFET

The electrical field and the current density near the drain region of MOS-FETs increase sharply with scaling down of the device. The hot-carrier effect becomes to have a significant impact on the MOSFETs with size in deep sub-micron and ultra-deep sub-micron region. The hot carriers with energy high enough may be injected into SiO₂ layer, which causes the generation of interface states, consequently results in the degradation of the parameters of the device. The dissertation studies the hot-carrier effect of small dimension nMOSFET thoroughly by theoretical analysis and computer numerical simulation. The problems, such as the mechanism of hot carriers generation and the device degradation, are focused on.Firstly, the classification of hot carriers, the mechanism of hot carriers generation, the formation of substrate current, and the saturation effect as well as temperature characteristics of device degradation are analyzed. Then the substrate current model is developed for deep sub-micron and ultra-deep sub-micron nMOSFET, based on the theories on substrate current generation. By computer simulation, it is given that the variety of the substrate current depending on the gate voltage,the drain voltage and the device structure. The simulation results agree well with the existing experimental data, which proves that the corresponding theories and the simulation are reasonable, and provides what relies on for one to predict the hot-carrier degradation in nMOSFET according to the variety of the substrate current.The appearance of drain current degradation means the existence of hot-carrier effect. According to the model of hot carriers breaking Si-H bond thus generating interface traps, this dissertation studies the mechanism of interface states generation and the relation between it and drain current degradation; and by simulation the dissertation obtains characteristics of drain current degradation. The results of this job indicate that drain current degradation changes for different work region. On the other hand, drain current degradation becomes saturation as stress time increases, which provides a reference to predict degradation of parameters in MOSFETs induced form hot carriers.