Reseach On Simulation And Application Of Si/SiO₂ Interface Structure Model

Si/SiO2 interface structure is one of the most important components of Si-based devices and integrated circuits, has critical impact on its performance. In the nano-scale, on the one hand, the transition region of Si/SiO2 interface structure have more significantly effect on the interfacial properties and the presence of defects in the Si/SiO2 interface structure decrease the gate dielectric reliably and device performance which required higher quality of the Si/SiO2 interface structure, on the othe hand, it’s difficult to accurately and comprehensively research on the interfacial structure and its defects only by experimental methods, and simulation has become an indispensable way to study the Si/SiO2 interface at the atomic scale. So it’s necessary to study and establish Si/SiO2 interface atomic structure model, and to study structural properties of transition region and the effects of interface defects on the electrical and optical properties at the atomic scale by simulation.The main results of experimental study and theoretical calculation of the Si/SiO2 interface characteristics was sorted. From the aspects of experimental study and modeling and simulation research on Si/SiO2 interface structure, the current research at home and abroad were summarized. As the deficiencies in simlation research of Si/SiO2 interface structure, we carried out the following tasks by using the first-principles simulation methods:1) The modeling methodes of Si/SiO2 interface atomic structure were researched. In terms of the structural properties of Si, SiO2 and transition region in Si/SiO2 interface structure, we sorted and summarized the defectes structure in Si/SiO2 interface structure, discussed the advantages and disadvantages of existing modeling methods, and then combined with the structural feature of Si/SiO2 interface structure, the methods to build Si/SiO2 interface atomic structure model were researched. As a result, we achieved an approach to build interfacial transition region and defects structure in the. Si/SiO2 interface atomic structure.2) To improve the accuracy of simulation calculations, optimization and selection of the parameters were resreached. In terms of the total energy, density of states, band structure, the exchange-correlation potential approximation,cut off energe(Ecutoff), Kpoint in the reciprocal space and geometry optimization parameters were optimized respectively.3) The research on modeling and characterization of Si/SiO2 interface transition region. Considering the structure of the silicon sub-oxide in interface transition region, a Si(100)/ SiO2 interface atomic structure model was established and optimized. After analyzed structural properties of interfacial transition region, we drawed conclusions that thickness of transition region is about 6 ?, Si-O bond length, Si-O-Si bond angle and O-Si-O bond angle in transition region were smaller than that in SiO2, and Si1+, Si2+ and Si3+ shaw different location distribution in transition region.4) The research on dielectric properties and optical properties of Si/SiO2 interface structure and its impact of defects. Considering different location and orientation of dangling bonds at interface, we established Si/SiO2 interface atomic structure models with a lateral dangling band, vertical dangling hanging and Pb0 defect respectively, and considering the hydrogen saturation to dangling bond by annealing process, established Si/SiO2 interface atomic structure model with hydrogen saturated dangling bonds. After structure optimization, we calculated dielectric and optical properties using CASTEP, inverstigated effects of interface defects on dielectric function and absorption coefficient by comparing simulation results of Si/SiO2 interface atomic structure models with and without interface defects, and then we obtained: in terms of the dielectric function, the horizontal dangling bonds, vertical dangling bond and Pb0 deffect increased the real part and the imaginary part of dielectric function when wavelength is greater than 800 nm, and these effects were eliminated substantially when the dangling bonds were saturated by hydrogen atoms; in terms of light absorption coefficient, the horizontal dangling bonds, vertical dangling bond and Pb0 defect increased absorption coefficient when the wavelength is 300 nm ~ 1000 nm, and Pb0 causesed absorption coefficient decrease when wavelength is within 200 nm ~ 300 nm, and the effects on 300 nm ~ 1000 nm wavelength absorption coefficient was eliminated when dangling bonds is saturated by hydrogen atom.This paper focused on the method of establishing the Si/SiO2 interface atomic structure model, optimized the key parameters in simulation, and analyzed the structural properties of transition region and discussed affects of interface defects on the dielectric and optical properties by first-principles calculation and simulation. This study will help to further establish Si/SiO2 interface atomic structure model for different proccess conditions, to research on formation process conditions of interface defect by combining with the experimental method to achieve controlling the defects in Si/SiO2 interface structure in the process. Meanwhile, it also help to explain and control the impact of Si/SiO2 interface structure and defects on device performance from the atomic scale, to further improve the quality Si/SiO2 interface structure and the performance of devices in applications.