| AVS 58th Annual International Symposium and Exhibition | |
| Surface Science Division | Tuesday Sessions |
| Session SS-TuP |
| Session: | Surface Science Poster Session |
| Presenter: | Boris Yakshinskiy, Rutgers University |
| Authors: | B.V. Yakshinskiy, Rutgers University R.A. Bartynski, Rutgers University |
| Correspondent: | Click to Email |
The contamination of optical surfaces in EUVL exposure tools, operating at 92 eV photon energy, results in degradation of the mirror reflectivity. We report studies of the thermal and electron-induced interaction of benzene and toluene vapors, typical background gases, with the Ru surface, as model cap layer for multilayer mirrors (MLM), using temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), electron stimulated desorption (ESD), low electron energy diffraction (LEED), and scanning tunneling microscopy (STM). A low energy electron source (100 eV) is used to simulate radiation excitations on the surface produced by EUV photons. Heating of adsorbed hydrocarbons leads to a stepwise dehydrogenation and buildup a self-limited carbon monolayer. Electron bombardment of the bare Ru surface in the presence of gas phase hydrocarbons inevitably results in rapid accumulation of 1 ML of carbon or carbonaceous species. Subsequent contamination growth is determined by the electron-stimulated surface chemistry on the graphitized surface. Graphene monolayer and bilayer formation on Ru(0001) by hydrocarbon pyrolysis or by carbon segregation from the sample bulk is examined as a possible way to reduce the surface contamination rate. Graphene buildup has been confirmed by the presence of corresponding superstructures in LEED patterns and STM images. The binding energy of the hydrocarbon molecule is found to be smaller on a graphene layer than on disordered carbon. Electron irradiation of both bare and graphene covered Ru surface in the presence of benzene and toluene vapors leads to C-buildup. However, in a case of low irradiation density, when the electron flux is rate-limiting parameter, graphene monolayer exhibits its protective properties by slowing down carbon accumulation initially, until sufficient thick overlayer is formed. But in a case of high electron flux, when the adsorption of hydrocarbons is rate-limiting parameter, the carbon accumulation rate is invariant to the surface morphology.
The work is supported by Intel and DOE.