Study Of Growth Kinetics And Defect Control For Si-based Strained Materials

Si-based strained materials and technologies with high mobility enhancement,flexible energy gap and full compatibility with standard silicon technology, are widelyused in high-speed, high-frequency, low-voltage and low-disspation applications,andbecome the critical technology that extends the Moore’s law in21stcentury. Applicationof Si based straine technology is based on preparation of high quality Si-based strainedmaterialand,thus mechanism of growth, growth kinetics and the growth process are themost critical factors in the preparation of Si based strained materials.With the FLUENT numerical analysis software, using CFD(Computational FluidDynamics) simulation methods, the distribution of chamber temperature, density, speedand pressure are simulated for the growth of Si-based strained and relaxed materials byRPCVD (reduced pressure chemical vapor deposition)process in this dissertation. Andfor the first time, orthogonal method is used for error, therefore,the optimized growthprocess parameters of RPCVD are obtained for Si-based strained and relaxed materials.Based on Dimer theory and the growth characteristics of SiGe alloy, thecomponent velocity mechanism and the discrete flux density mechanism of Si-basedstrained and relaxed materials are presented in this dissertation. Furthermore,based onthe gas collision theory, the surface reaction growth rate model of Si-based strainedmaterials by CVD (chemical vapor deposition) are built. Finally, based on the discreteflow density model, component velocity model and Grove theory, the CVD growthkinetics model and relevant optimization model are built for Si-based strained andrelaxed materials, compared with experimental data, the proposed model has betteragreement than surface reaction growth model.The defect mechanism and behaviors of Si-based strained and relaxed materials aresystematically investigated in this dissertation. According to the process principle oflow temperature Si buffer, graded SiGe buffer and ion implantation, three materialstructures and processes to control TDD (Threading Dislocation Density) of strained Simaterial are designed. The material characterization results prove that these structureshave lower TDD compared with normal structures.With Flunt optimized simulation process parameters, the growth experiments ofSi-based strained and relaxed materials are investigated by RPCVD. Using AFM, DIC,Raman and TEM, material performance and characteristics, such as surface roughness,surface dislocation density, stress and strain, Ge component and dislocation behavior,are completely and systematically characterized.Based on elastic mechanics theory and mechanical property of SOI materials, a new method of fabricating wafer level uniaxial strained SOI wafer is proposed and theprocess principle of this new method is explained. Uniaxial strained SOI wafer has beenprocessed and the strain values is higher than present uniaxial tensile strained SOI waferusing similar technology.On the foundation of Schr dinger’s equation and k.p perturbation theory, thevalence band dispersion relation model of strained Ge/Si1-xGexis also built, whichapplies to any crystal orientation of (001),(101) and (111) plane. And the correspondingvalence band structure and the anisotropic and isotropic effective mass of holes are alsocalculated.