Ultra-High Spatial Resolution SEM EDS of Semiconductor Devices

Elemental Mapping of Semiconductor Features using a SEM

Typically ultra-high spatial resolution elemental distribution maps are acquired using a transmission electron microscope alongside Energy Dispersive Spectrocopy (TEM EDS) or Electron Energy Loss Spectroscopy (EELS). However, the acquisition of TEM-like EDS maps is also possible using a field emission gun scanning electron microscope (FE-SEM) equipped with an EDS detector, provided that the detector offers a high collection efficency.

Here we present the unique capability of Bruker’s XFlash^® 7100oval 100 mm² windowless detector for the acquisition of ultra-high spatial resolution SEM EDS elemental maps.

In order to take high-resolution measurements and to resolve fine features, the electron beam divergence and footprint must be kept to a minimum. This is achieved by lowering the probe current to a few tens to a maximum of a few hundreds of pA to minimize columbic repulsions. Such conditions are suitable for imaging at high spatial resolution, but not ideal for analytical measurements such as EDS, since the X-ray fluorescence generated at low probe currents is also very low.

Bruker's 100mm² windowless EDS detector with an oval-shaped SDD chip is designed for maximum collection efficiency at the low probe currents required for EDS SEM analysis on the nanoscale.

Using the XFlash® 7100oval it is possible to acquire TEM-like EDS, or STEM-in-SEM, measurements of thin cross section samples such as shown in figure 1 and figure 2.

Discover XFlash 7100Oval Contact an expert

Figure. 1: Ultra-high resolution SEM EDS map of a 30 nm thin FIB/TEM lamella showing the distribution of elements within a FinFET fin-structure. The high-k dielectric spacer layer HfO is resolved at a EDS spatial resolution of 2 nm. Additionally, the overlapping peaks of Si-K, W-M and Hf-M X-ray lines have been automatically deconvoluted.

Fig. 2: SEM EDS map of a FinFET device in gate-cut geometry showing the complex elemental distribution of a FinFET structure.

Fig. 3: Strong peak overlaps of Si-Kα (1.74 kV), W-Mαβ (1.802 kV), Hf-Mαβ (1.671 kV) and Ta-Mαβ (1.737 kV) X-ray lines are automatically deconvoluted.