Electron irradiation-based cleaning of the scanning electron microscope and its samples

Abstract

The deposition of carbonaceous material under electron beam irradiation is an old and persistent problem in scanning electron microscopy. It impedes high-resolution imaging and measurements, especially at the nanometer scale. The emergence of contamination is a complex process of adsorption, dissociation, and desorption of carbonaceous molecules. Depending on the kind and amount of precursor molecules, vacuum, sample material, temperature, and the intensity and energy of the irradiating electrons, deposition can overwhelm removal or the other way. Fortunately, with the introduction and commercial availability of low-energy, plasma-based, and other cleaning devices, contamination can be reduced to non-detectable levels. Plasma devices, working in low vacuum, which is necessary to start and sustain plasma generation, can effectively remove contamination precursor hydrocarbon molecules to the extent that a clean sample can be imaged and continuously measured for hours without deposition of any perceptible amount of carbonaceous contamination. Here, we report on the results of a new and effective cleaning device that has recently become available, which is different from plasma cleaning devices. It is based on low-energy electron irradiation and works in high and ultra-high vacuum (UHV).