The sputtering yield of crystalline Si(1 0 0) surface by monoatomic and diatomic nitrogen ions impact

Abstract

We have investigated the sputtering rate of thin crystalline silicon film forming silicon-on-insulator structure impinged by atomic and molecular nitrogen ions with medium energies of 25, 50, and 100 keV/(N atom) at several incident angles of 0, 30, 45, and 60°. The thickness of the surface silicon layer after ion irradiation was quantitatively estimated by Rutherford backscattering spectroscopy using 2.56-MeV 10B2+ ions with a grazing angle geometry to accurately analyze the thickness decrement in several nanometers for ultrathin Si layers. The sputtering rates were compared with a full-cascade TRIM simulation based on a binary collision approximation. We found that the sputtering yields of monoatomic N ion with higher energies (>50 keV/N) took significantly higher than that of diatomic N2 ion, probably suggesting that a wake-like effect of relatively fast NN molecular ions surviving for a long period due to a considerably strong triple bond. In addition, the observed sputtering yields for all present conditions were a few times smaller than that estimated by the full-cascade TRIM calculation using typical lattice parameters. We quantitatively discuss the details of sputtering phenomenon of crystalline silicon by nitrogen ions at medium energy region.