EELS ELEMENTAL MAPPING OF A DRAM WITH FE-TEM

The elemental distribution in an oxide-nitride-oxide (O-N-O) dielectri c multi-layer in a dynamic random access memory (DRAM) device has been investigated by elemental mapping using an electron energy-loss spect rometer (EELS) combined with a field-emission (scanning) transmission electron microscope (FE-(S)TEM). The O-N-O layer is designed as an ins ulator between a single-crystal silicon substrate and a poly silicon c apacitor. The nominal structure is an amorphous SiO2-Si3N4-SiO2 phase. Two different approaches, utilizing both EELS point analysis and ener gy-filtering transmission electron microscopy (EF-TEM), were made to c onstruct the concentration profiles of low- and medium-atomic-number e lements, N, O and Si. Further, the relative quantities of N, O and Si atoms were processed to calculate the theoretical contrast due to high -angle electron scattering from these atoms. The calculated contrast a greed fairly well with the experimental contrast obtained by high-angl e annular dark-field (HAADF) STEM.