研究目的
To analyze the influence of pore size and porosity on structural changes in low-k OSG dielectrics under low-energy Ar ion irradiation using molecular dynamics simulations.
研究成果
MD simulations show that nanoporous structures with small pores and low porosity undergo pore collapse and form a continuous solid layer under low-energy Ar ion irradiation, reducing sputtering yield to that of solid material. Larger pores and higher porosity enhance sputtering due to surface curvature and show minimal structural changes. Thermal stability studies reveal that excess surface energy per unit volume is a key parameter, with a threshold of ~1.0 eV·nm?3 for pore collapse. The findings provide insights into plasma processing of low-k dielectrics and highlight the importance of porosity and pore size in material response to irradiation.
研究不足
The study uses silicon models as analogues for OSG films, which may not fully capture the complexity of real low-k materials. The computational resources limited the number of impacts and models simulated. The choice of empirical potentials could affect results, and the simulations assume neutralized Ar ions, which might not reflect all plasma conditions.
1：Experimental Design and Method Selection:
Molecular dynamics (MD) simulations were used to study sputtering from nanoporous silicon-based models with varying porosity and pore sizes under low-energy (200 eV) Ar ion irradiation at normal incidence. The Stillinger-Weber potential described Si-Si interactions, and the Molière potential described Si-Ar and Ar-Ar interactions.
2：Sample Selection and Data Sources:
Models were built as structural analogues of CVD and SOG low-k films with porosities of 22% and 44% and pore radii from
3：8 to 8 nm, based on a crystal silicon (001) surface with 64,000 atoms. List of Experimental Equipment and Materials:
Computational models were created using LAMMPS software on HPC resources; visualization and analysis used OVITO software.
4：Experimental Procedures and Operational Workflow:
Simulations involved successive Ar ion impacts (up to 5000 ions) with damage accumulation, temperature control via Berendsen thermostat, and heating from 300 K to 4000 K using the Noze-Hoover thermostat. Sputtering yield was calculated based on ejected Si atoms.
5：Data Analysis Methods:
Specific surface area (SSA) was calculated using the alpha-shape method in OVITO; local temperature and potential energy per atom were analyzed to study structural changes and pore collapse.
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