Analysing interface reactions using EELS

Using EELS spectrum imaging, an HfN or Hf(O,N) reaction layer has been identified at the TiN/HfO2 interface in a metal inserted high-k gate stack. The reaction layer has a mean thickness of 0.45nm over an 18nm length of the interface. This reaction layer formed in the original HfO2. By binning the data ×4 along the interface, a variation of the width from 0.35nm to 0.65nm along the interface can be seen. The 10%-90% widths of the elemental profiles can also be found but the binning required is greater (×10). The profile widths are approximately constant along the interface but the values differ from element to element. Thus the reaction has not formed a conformal layer of uniform thickness. An efficient way of processing the data at different levels of binning is described.