Scanning electron microscopy (SEM) is widely used to produce images of nanostructures by scanning the surface of the sample with a focused electron beam. The electron beam interaction with the sample produces various electron and x-ray signals at different depths of the sample. Secondary electrons (SE) only escape from the top few nanometers of the surface of a sample due to their low energy and short mean free path characteristic in solid matter. Past studies have reported small temperature effects on SE yield in different materials. Furthermore, during the electron-substrate interaction, heat is also generated and this makes it possible to apply the e-beam as a high-quality mobile heat source for generating nanoscale thermal hotspots.
In this work, I first describe my studies of the e-beam heating effect from the SEM on suspended silicon nitride (SiNx) thin films with thickness ranging from 200 to 500 nm using micro-fabricated calorimeter devices inside a standard SEM. The results validate the absorption energy profiles calculated using Monte Carlo (MC) techniques by CASINO in Chapter 2. Then, the secondary electron yields from polycrystalline silicon as a function of temperature using SEM imaging have been studied with the assistance of CASINO in Chapter 3 and 4. This study guides us to a path of sub 100 nm spatial resolution thermometry technique using widely available hardware, overall this approach demonstrated and validated the SEM thermometry technique using SE intensity change at ~100 nm scale resolution, which is far finer than the previous demonstration by Khan et al. (JAP, 2018) which had averaged over much larger, ~500 m by 500 m, area. These results will help develop the application of the e-beam as an advanced nanoscale mobile heating source and secondary electron signal as temperature signal for future thermal metrologies at the micro and nanoscale (Chapter 5).
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