Compositional Analysis of an IC Chip's Surface and Substructure

SEM EDS analysis with the XFlash 7^® EDS detector can be used for the compositional analysis of both a semiconductor's surface and substructure. 

An X-ray signal is generated when an electron beam interacts with material. This interaction typically occurs a few microns below the sample surface and forms a so-called interaction volume or excitation volume where X-rays are generated. In the case of SEM EDS the interaction volume depth depends on the acceleration voltage (in kV) of the SEM and the average atomic weights of the elements present in the sample. Typically, a high acceleration voltage (e.g. 20 kV) generates X-rays from a large excitation volume of a few microns, meaning X-rays are emitted from deeper within the sample, whereas a low acceleration voltage (e.g. 3 kV) generates X-rays from a small excitation volume of only a few 100 nanometers from the sample surface.

This application example demonstrates that, by using different acceleration voltages from low to high kV (3, 5, 10 and 20 kV), SEM EDS analysis can be used to resolve the surface and depth features of an Integrated Circuit (IC) chip (Figure 1a and Figure 1b).

The acquired elemental distribution maps of the IC chip's surface and substructure revealed that cobalt, germanium and hafnium were present at the surface of the chip, whereas tungsten and titanium were found deeper within the structure.

Automatic deconvolution of the overlapping EDS peaks of Tungsten, Silicon and Hafnium at each acceleration voltage was carried out using Bruker's ESPRIT software. As shown in this video, and in the images below, ESPRIT's deconvolution algorithm makes it possible to identify and resolve even strongly overlapping elements, across a range of acceleration voltages.