The recent massive adoption of nanotechnology has triggered a race for the highest resolution in Scanning Electron Microscopy (SEM). One approach for achieving the ultimate spatial resolution uses a Magnetic Immersion Lens. Previously, the use of an immersion lens made orientation mapping impossible. This is because the magnetic field created by the lens interferes with the Transmission Kikuchi Pattern (TKP) collection and analysis process. The interference has two major components:
First, the Kikuchi signal is reduced to a region expanding up to 10 mm from the optical axis of the SEM. This containment of electrons around the optical axis means that very few scattered electrons will reach a standard EBSD detector which typically places its phosphor screen at distances greater than 15 mm from the optical axis of the SEM. On-axis TKD technique enabled by OPTIMUS 2 solves this issue by capturing the Kikuchi patterns from around the SEM optical axis.
Second, the heavy distortions created by the magnetic field’s presence in the TKPs, render impossible an accurate band detection. To correct the distortions and compensate for the rotations and shifts in the TKPs, we have developed a new software feature (patent pending) called ESPRIT FIL TKD (Full Immersion Lens TKD). The feature is easy to calibrate and has been fully integrated in the automatic map acquisition process of ESPRIT 2 software.
The combination of FIL TKD feature with on-axis TKD makes possible accurate orientation mapping using high-end FE-SEMs while operating in their ultra-high resolution mode, i.e. with the immersion lens active.
The end result or benefit of this unique combination of HW & SW options is clearly visible in the TKD results shown in Fig. 2 (*). The Pattern Quality maps (left) demonstrate qualitatively that the physical spatial resolution is far better when activating the immersion lens (much sharper features). Grains/features finer than 10 nm can be clearly seen in the orientation map acquired with the immersion lens active.
(*) The results presented here should be taken qualitatively and not as a resolution specification of our TKD solution and/or that of a certain brand of SEMs. The difference in TKD map resolution and indexing quality between immersion and non-immersion modes of relevant SEMs may vary depending on the model and/or make as well as the room environment, e.g. temperature, ground vibrations, acoustics, etc.