研究目的
Investigating the sputtering yield of crystalline Si(100) surface by monoatomic and diatomic nitrogen ions impact at medium energies.
研究成果
The sputtering yield for atomic N ions exceeded that for molecular N2 ions at higher energies, likely due to the strong triple bond in N2 molecules prolonging their lifetime and causing wake-like effects. Experimental sputtering yields were significantly smaller than TRIM simulations, indicating that conventional surface binding energy values (e.g., 4.7 eV) may be underestimated, with plausible values around 20-30 eV for crystalline Si(100). Further research is needed to clarify the factors behind this discrepancy.
研究不足
The study is limited to nitrogen ions and crystalline silicon at medium energies; results may not generalize to other ions or materials. The discrepancy between experimental and simulated sputtering yields suggests potential inaccuracies in physical parameters used in simulations. High ion fluences could introduce artifacts, though efforts were made to minimize them.
1：Experimental Design and Method Selection:
The study used Rutherford backscattering spectroscopy (RBS) with
2：56-MeV 10B2+ ions to measure thickness decrement in silicon-on-insulator (SOI) samples after ion irradiation. A full-cascade TRIM simulation based on binary collision approximation was employed for comparison. Sample Selection and Data Sources:
Wafer-bonded SOI wafers from SOITEC Co. Ltd. with ultrathin Si(100) film of
3：4 nm thickness on a buried SiO2 layer were used as target samples. List of Experimental Equipment and Materials:
Medium-current ion implanter (ULVAC Co. Ltd.), Faraday cups for beam current monitoring, 1-MV Pelletron accelerator with SNICS source for RBS, Si-surface barrier solid state detector, atomic force microscope (AFM), and RBS simulation program (SIMNRA).
4：Experimental Procedures and Operational Workflow:
N+ and N2+ ions were implanted at energies of 25, 50, and 100 keV/(N atom) and incident angles of 0°, 30°, 45°, and 60° with low current density to avoid temperature increase. Beam current was monitored using Faraday cups. Post-irradiation, RBS was performed with 10B2+ ions at a tilted angle to avoid channeling, and surface morphology was observed with AFM.
5：Data Analysis Methods:
RBS spectra were analyzed using SIMNRA to fit and determine sputtering yields. Results were compared with TRIM simulations, adjusting parameters like surface binding energy and displacement threshold energy.
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