In Situ Time-of-Flight Mass Spectrometry of Ionic Fragments Induced by Focused Electron Beam Irradiation: Investigation of Electron Driven Surface Chemistry inside an SEM under High Vacuum

Abstract

Recent developments in nanoprinting using focused electron beams have created a need to develop analysis methods for the products of electron-induced fragmentation of different metalorganic compounds. The original approach used here is termed focused-electron-beam-induced mass spectrometry (FEBiMS). FEBiMS enables the investigation of the fragmentation of electron-sensitive materials during irradiation within the typical primary electron beam energy range of a scanning electron microscope (0.5 to 30 keV) and high vacuum range. The method combines a typical scanning electron microscope with an ion-extractor-coupled mass spectrometer setup collecting the charged fragments generated by the focused electron beam when impinging on the substrate material. The FEBiMS of fragments obtained during 10 keV electron irradiation of grains of silver and copper carboxylates and shows that the carboxylate ligand dissociates into many smaller volatile fragments. Furthermore, in situ FEBiMS was performed on carbonyls of ruthenium (solid) and during electron-beam-induced deposition, using tungsten carbonyl (inserted via a gas injection system). Loss of carbonyl ligands was identified as the main channel of dissociation for electron irradiation of these carbonyl compounds. The presented results clearly indicate that FEBiMS analysis can be expanded to organic, inorganic, and metal organic materials used in resist lithography, ice (cryo-)lithography, and focused-electron-beam-induced deposition and becomes, thus, a valuable versatile analysis tool to study both fundamental and process parameters in these nanotechnology fields.

New precursors for direct writing of nanostructures using charged particle beams

“…75,83,[288][289] But the assumption of a carbide formation for the tungsten deposits is mainly based on their composition and electrical transport characteristics. 23 However, recent in situ MS experiments during the FEBID deposition of W(CO)6 did show significant amounts of carbide-type WCx + /WC(CO) + signals, 184 in good agreement with single collision experiments. 290 Furthermore, freestanding 3D rods deposited with FEBID showed SAED patterns corresponding to pure W as well as W2C and W3O.…”

“…183 Additionally, the evolution of volatile fluorocarbons has been observed by MS when pieces of solid precursor of both Cu2(µ-O2CC2F5)4 and Ag2(µ-O2CC2F5)2 were irradiated with electrons. 184 An overview summarizing the different homometallic precursor classes is presented in Figure 10. Based on the experimental data available up to date carbonyls and hydrides are still the best classes of ligands when targeting high metal content in FEBID.…”

Ice lithography using tungsten hexacarbonyl

“…We were not able to reliably measure the W:C:O ratios, because the tungsten EDX spectrum was overlapping with the substrate Si EDX spectrum. To have a more thorough understanding of the cross-linking process, other techniques can be necessary, e.g., mass spectrometry [28,29] and in-situ spectroscopic ellipsometry [30].…”

Condensed Matter Systems Exposed to Radiation: Multiscale Theory, Simulations, and Experiment

“…Apart from established experimental techniques for monitoring the FEBID/FIBID deposits, new approaches have been developed to bring insight into the deposition process. One example is the focused electron beam-induced mass spectrometry (FEBiMS) technique, 507 which enables the analysis of charged fragments generated on the substrate at real-time FEBID conditions without postirradiation. Data obtained in such experiments can be used to validate the MM predictions for the irradiation phase of the deposition process.…”