Developments in nanotechnology, together with the relentless scaling of semiconductor devices, have placed increasing emphasis on our understanding of thin films and interfaces, both in terms of their structure and chemistry.
In this work, the compositional and structural variations in 5nm erbium oxide thin films grown on Si substrate have been studied using a combination of high resolution electron microscopy (HREM), electron energy loss-spectroscopy (EELS) and energy-filtered TEM (EFTEM). The work has been carried out using a JEOL 3000F field emission gun TEM.
HREM imaging has been used to determine the structure and thickness of the layers, and to estimate the roughness of the interfaces. HREM revealed the formation of an interfacial layer. In the stack system, the crystalline/amorphous (c/a) interface is difficult to analyse since the HREM imaging process smoothes out the position and roughness of the interface along the beam direction.
The chemical information may be more conveniently visualized by generating EFTEM images of constituent elements. To observe the elemental distribution within a Si/SiO2/Er2O3 stack, the EFTEM images were acquired for erbium N4,5-edge, erbium M4,5-edge, oxygen K-edge and silicon L2,3-edge using the standard 3 window method and the optimum elemental mapping parameters calculated by use of a reference spectrum. The reliability of the EFTEM mapping information has been investigated in terms of the spatial resolution of this technique.
A combination of HREM imaging and EFTEM elemental mapping provides valuable insight into the structure and composition of thin films and interfaces, which is an essential step in the future development of semiconductor devices.
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