Electron-beam induced deposition and etching using bulk liquid reactants yields high-purity metal nanostructures (e.g. Pt, Au, Cu, and Ag), introduces new possibilities for depositing alloys and compounds (e.g. AuPt, AuAg, and CdS), and  enables processing of materials for which there are no simple gas-phase precursors (Ag) or volatile etch products (Cu).  These processes can be conducted on membranes in sealed liquid cells under high vacuum or on bulk substrates in environmental scanning electron microscopes (SEM).  However, there has been little work on modeling liquid-phase processes and the relative importance of potential mechanisms (primarily radiation- and electro- chemical) remains unclear.  Here we present a hybrid model in which electron Monte Carlo simulations are coupled with continuum finite-element calculations.  The Monte Carlo model tracks electron interactions with the liquid and solids, including secondary electron emission, and provides electron energy loss as a function of position.  This becomes the input to a finite element model that accounts for radiolysis in the liquid, subsequent reactions, mass transport, and movement of the liquid-solid interface.  Here we examine the specific case of radiation-chemical etching of copper films on silicon substrates in aqueous sulfuric acid solutions.  We calculate etch rates based on the radiolytic generation of sulfate radicals, the subsequent formation of peroxydisulfate ions, and the oxidation of copper by both species.  Calculated rates are compared with experimental results obtained from etching electroplated copper films in an environmental SEM. <br/>

Hybrid Monte Carlo and continuum modeling of electron-beam induced processes using liquid reactants

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.