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Abstract

The sputtering yield, the spatial distribution of the sputtered atoms, the energy distribution and the average energy of the sputtered atoms are important for numerous deposition techniques, as they determine the microstructure and the physical properties of the thin films. Using SRIM (Stopping and Range of Ions in Matter) simulations, I investigated the influence of different parameters (surface binding energy, incident ion energy, mass of target atoms) for a numerous set of target materials, relevant to sputtering: B, C; Al, Si; Ti, V, Cr, Cu; Zr, Nb, Mo, Ag; Hf, Ta, W, Au. The incident Ar ion energies ranged from 300 to 1200 eV, both for normal and oblique ion incidence.
The total sputtering yield showed notable trends according to the element position in the periodic table. Group 4 elements exhibited the lowest sputtering yields that increased with group number in periodic table. The angular distribution of sputtered atoms revealed a cosine distribution for transition metals. The oblique ion incidence showed asymmetric distributions at lower ion energies with greater symmetry at higher energies.
We conducted a systematic investigation into the influence of surface binding energy, atomic mass, and ion energy on the total sputtering yield. These parameters were analyzed in relation to analytical equation derived by Sigmund. Due to the differences between the existing analytical model and SRIM simulations, we suggested a new modified equation. Our modification introduced a power fitting parameter, accounting for the non-linear dependency of the sputtering yield on the ion energy. The equation provides reliable estimates for sputtering yields at ion energies up to 1200 eV.
The energy distribution functions (EDFs) of sputtered atoms were investigated for the same selection of elements as the sputtering yields. SRIM simulations of EDFs for transition metals and light elements were compared to the analytical equations for EDFs derived by Sigmund and Thompson and with experimental data from the literature. The simulated EDFs provided realistic results for transition metals but were incorrect for elements lighter than Si. All EDFs exhibited a low-energy peak near one-half of the surface binding energy and a high-energy tail decreasing as E−2. Variations in EDF characteristics, such as peak positions and full width at half maximum (FWHM), were observed concerning atomic number, ion energy, and periodic table group.
An empirical equation for transition metals was established to estimate the average energy from the sputtering yield ‒ the average energies of sputtered atoms are inversely proportional to the sputtering yield, with transition metals exhibiting the highest average energies and group 11 elements displaying the lowest.
Although the thesis is primarily aimed to compare the analytical model and Monte Carlo simulations for sputtering processes we also performed measurements of sputtering yield for Ti, V, Cr, and Cu and compared them with simulated values. Notably, deviations between SRIM simulations and experimental total sputtering yields were most pronounced at lower Ar ion energies. While Cu and Cr demonstrated agreement with simulations above 100 eV, disparities were more significant for V and Ti. Additionally, the differential sputtering yields were measured. The highest differential sputtering yields were observed at 40°−50° angles, decreasing with emission angles.