THE EFFECTS OF NONUNIFORMITY ON THE MODELING OF RESISTIVITY IN POLYCRYSTALLINE SILICON THIN FILMS (POLYSILICON, GRAIN BOUNDARY, DISTRIBUTION FUNCTION, DOPING PROFILE, TEM).

摘要

This research is concerned with the electrical and transport properties in the Low Pressure Chemical Vapor Deposited (LPCVD) polycrystalline silicon thin film resistors. There are currently many uses of polysilicon in the integrated circuit industry, but these uses are constrained by the lack of control over the electrical properties of this material. This problem is a direct result of the nonuniformity in the physical nature of this material. Current models of the electronic properties involve detailed analysis of the abstract conduction mechanisms while ignoring the more realistic aspects of the observed characteristics. This research attempts to provide a new theory of practical use for the modelling of the characteristics of this material. The theory developed by this study explicitly models the nonuniform characteristics by the use of distribution functions. The model is also applied to characterize the experimental results of the electrical properties of variously processed LPCVD polysilicon. The study also develops a procedure for the determination of the location of the charge subsets by extraction from experimental results. Included in the study is an investigation of the microstructure by Transmission Electron Microscope.; The theory developed by this investigation is applied to the evaluation of the resistivity function of temperature for polycrystalline silicon thin film material. The derived function includes the effects of the variation in grain boundary barrier heights, the grain boundary surface to volume ratio, a carrier density which is constant with temperature and the thermionic emission conduction mechanism. Also, the calculation of the amount of charge trapped at the grain boundaries is modified to include the effect of a dopant profile near the grain boundary. All parameters in the model are constants with temperature and are determined from experiment.