| Si-based strained technology can enhance the historical performance underappropriate stress and make it compatible with traditional silicon processing, especiallyfor uniaxial-process-induced stress being adopted in nearly all90,65, and45nmtechnology nodes for both microprocessor and consumer products. It has extensiveapplication prospect in high-speed and high-property semiconductor devices andintegrated circuits. The key feature to enhance device performance is valence bandwarping. A systematic study of valence band structure has essential theoreticalsignificance and practical value.This paper is focus on the uniaxial strained Si material. On the basis of straintensor models created, the strain tensor for the uniaxial strained Si material alongarbitrarily direction in the (001),(101) and (111) typical surfaces is analysed. Using theperturbation method to find the approximate solution of the Schrodinger equation, withthe frame of K P theory, the valence band structure model has been established bytaking strained Hamiltonian perturbation into account. It is applicable for the strained Simaterial on arbitrarily surfaces and direcrtions.Based on valence band structure model observed, taking strained Si relatedparameters into account, valence band structure in uniaxial strained Si is analysed. Theresults are obtained such as the energy level of first valence band, second valence bandand spin-orbit splitting band at the Γ position, splitting energy, energy distributionalong arbitrarily k wave vector directions and constant energy surface. They areessensail to the investigation into the mechanism of performance enhancement.Furthermore, based on unstressed Si material, a comparison between biaxial anduniaxial strained Si on valence band warping affecting hole mobility is given. The resultcan provide theoretical basis for the application and devices design for Si-based strainedmaterials. |
