Secondary Electron Energy Contrast of Localized Buried Charge in Metal–Insulator–Silicon Structures

Abstract

This paper presents a new method for creating and monitoring controlled localized negatively charged regions inside insulators with a scanning electron microscope (SEM). A localized buried charged region is created and observed close to the point where a high voltage primary beam (10 kV) strikes a metal–insulator–silicon specimen. The amount of buried charge within the insulator at any given moment can be dynamically monitored by detecting the appearance of a second peak in the secondary electron (SE) energy spectrum. SE energy spectral signals were obtained through the use of a compact high signal-to-noise energy analyzer attachment that was fitted on to the SEM specimen stage. An electrostatic model, together with Monte Carlo simulations, is presented to explain how the SE charge contrast effect functions. This model is then experimentally confirmed by using the SE energy spectral signal induced by a gallium ion beam inside a dual focused ion beam-SEM instrument.

Quantitative material analysis using secondary electron energy spectromicroscopy

“…The technique was previously reported as a means of improving the analyser output signal-to-noise ratio, and making the SE peak narrower and more symmetric. It was used to enhance dopant contrast and surface/trapped charge contrast [45][46][47][48] . Figure 1e,f demonstrate how biasing the specimen and its surrounding electrode by − 10 V in this context is similarly capable of enhancing material contrast information at a primary beam voltage of 1 kV, causing the negatively biased Au spectral signal height to be greater than the one for Pt, while making the Pt spectral signal broader than the Au spectral signal, overcoming the inconsistent results of the unbiased case shown in Fig.…”

“…The work reported here utilises a small wide-angle electric toroidal energy analyser SEM attachment design 29 , which has formerly been used to track small changes in the SE energy spectral signal shape for applications such as quantifying dopant concentration 45,46 and mapping interface/surface charge distributions 47,48 . It is used here to perform quantitative material analysis in a variety of different ways.…”

Non‐Destructive Tomographic Nanoscale Imaging of Ferroelectric Domain Walls

“…the bound charges that acts on the secondary electrons via electrostatic induction and, hence, influences the secondary electron yield. [53] It is important to note, however, that the SEM contrast formation is highly non-trivial in ferroelectrics with multiple possible contributions; [28] to clarify the microscopic origin, additional studies are required, which is beyond the scope of this work.…”

The Design of a Reflection Electron Energy Loss Spectrometer Attachment for Low Voltage Scanning Electron Microscopy

“…However, there will also be a corresponding gain in signal-to-noise performance. This gain in signal-to-noise has proved very useful for applications where only changes in the SE energy spectral shape need to be quantified [13][14][15]. The acceleration SE mode of operation in the present analyzer design can readily be implemented electronically by changing the values of V B and V D .…”

“…The research work presented here follows from the recent success of using secondary electron energy spectroscopy (SEES) inside an SEM for various different material analysis applications. SEES was successively used to acquire bulk valence band density of states Materials 2021, 14, 7511 2 of 14 information [12], characterize semiconductor wafers and measure dopant concentration distributions [13], and track the build-up of charge in samples having insulator layers [14,15]. These achievements were made possible by using a compact high signal-to-noise secondary electron (SE) toroidal electrostatic sector energy analyzer attachment, small enough to fit on to an SEM's specimen stage [16][17][18].…”