CHARACTERIZATION OF POLYCRYSTALLINE SILICON WITH ELECTRON BEAM INDUCED CURRENT MICROSCOPY AND DEEP LEVEL TRANSIENT SPECTROSCOPY

This research is focused on determining either dislocations or impurities degrading polycrystalline silicon. 1% Metallurgical Grade (MG) P-type polycrystalline silicon cut from the middle of an ingot grown by Bridgman method at lowering rate of 1 cm/hr has been characterized with Electron Beam Induced Current (EBIC) microscopy and Deep Level Transient Spectroscopy (DLTS). Schottky diode arrays have been made by evaporation on this polysilicon material instead of p-n diodes which involved high temperature processes. Two bands of hole (majority) trap energy levels have been found on DLTS spectra. We concluded that these traps are introduced by dislocations instead of impurities which have discrete energy levels. These results are in agreement with the x-ray topography measurements.; The main contribution of this research lies in presenting a method which enables us to tell either dislocation traps or impurity traps is dominant in polycrystalline silicon.; A DLTS system with a spectrum analyzer has been developed during this research. Theoretical analysis and supporting experiments have been done to show that this method, which is faster and more accurate than other methods, is able to measure the time constant of any exponential waves.; Also a simplified model is presented to explain the variation of the electron beam induced current as a function of distance measured from the grain boundary. From this model, the surface recombination velocity of a specific grain boundary can be determined.