Contribuição a simulação computacional do processo de LPCVD




This work deals with the study and simulation of LPCVD-Low Pressure Chemical Vapour Deposition- a basic process for thin film deposition. The reaction of silicon deposition by silane pyrolisis is adopted for its simplicity and importance without sacrifieing the quality of treatment. To begin with, we present the atmospheric presure CVD technique in the light of the boudary layer theory. Later we discuss the LPCVD process. The texture of the film deposited and the micromechanisms of the said reaction are analysed, as a function of the inputs. Using the derived equations, we identify the main factors that influence the axial homogeneity (wafer to wafer) as well as the radial homogeneity (within the wafer) df the deposited filmo Assuming the restrictions: i) there is no radtial temperature gradient, ii) the growth is limited by surface kinetics, and iii) transport is due to a laminar flow in the annular region and gaseous diffusion in the space intra-wafers, an interesting model is sugested to the simulation of the batch type, hot wall, LPCVD reactor, taking into account: (a) the empty inlet tube, (b) the molar expansion of the gas, and (c) the depletion of reactants along the main flow direction. The developed method of simulation provides satislactory results with reduced computer processing time and a rather simpler mathematical evaluation when compared with proposed models in literature, using the same restrictions and conditions. Finally, the future trends in CVD processing are in brief presented. They point to single wafer, cold wall, photo- and plasma assisted systems with in situ measurements and intense computerized control


simulação (computadores) semicondutores

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