The role of electron scattering in electron-induced surface chemistry

Electron-induced chemistry on surfaces plays a key role in focused electron beam induced processing (FEBIP), a single-step lithography technique that has increasingly gained interest in the past decade. It is crucial for the understanding and modelling of this process to know the role of the surface in the electron-induced dissociation of an adsorbed precursor molecule. However, the electron scattering in the underlying solid makes it impossible to determine this directly. In this paper the contribution of electron scattering in the target on the measured deposition yield is calculated for the precursor MeCpPt(IV)Me-3, using the matrix inversion method. The calculation is based on experimental data for the dissociation yield and secondary electron emission. Two trends are observed in the analysis. Firstly, the contribution of electron scattering to the experimentally determined dissociation yield is not dominant for primary electron (PE) energies up to about 50 eV. Therefore, the role of the surface in this energy range can therefore reasonably be deduced from differences between electron-induced dissociation in the gas phase and the adsorbed phase. Secondly, at PE energies above 80 eV the electron scattering contributes significantly to the measured dissociation yield. The cross section that is calculated with the matrix inversion method peaks at 80-150 eV, which is typical for gas phase ionization. This suggests that surface interactions (other than electron scattering) do not dominate the chemistry for energies above PE energies of 80 eV. The obtained result can be used as input for Monte Carlo simulations for focused electron beam induced deposition.