摘要
The effect of deposition pressure in controlling nanotwin formation and the associated properties of sputtered Cu thin films was systematically investigated over a wide pressure range (1.0–4.0 mTorr). Although nanotwinned Cu films have been widely studied, the pressure-dependent growth conditions governing nanotwin formation and their coupled effects on microstructure and functional properties remain insufficiently understood. The results in this work reveal a strong correlation between deposition pressure and growth behavior of nanotwinned Cu films. Films deposited at 1.5–2.0 mTorr exhibited strong (111) texture and dense nanotwinned structures, reaching a maximum twin density of 62 twins/μm2 and a peak hardness of ~3.2 GPa. Increasing the pressure to ~2.5 mTorr significantly reduces residual stress to ~41 MPa and improves surface planarity with a roughness of ~5 nm, indicating a balanced adatom mobility and energy flux during film growth. Despite the substantial microstructural evolution, the electrical resistivity remains nearly unchanged (~1.9–2.2 μΩ·cm). These results identify a practical deposition-pressure window (~1.5–2.5 mTorr) that simultaneously optimizes nanotwin density, mechanical performance, and surface planarity, providing a clear process-structure-property framework for engineering sputtered Cu thin films for advanced interconnects and direct metal bonding applications.
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•Nanotwinned Cu films formed under optimal sputtering pressure of 1.5–2.0 mTorr.•Deposition pressure governs twin density, texture, and stress evolution.•Strong (111) texture and dense twins achieved under energetic growth regime.•Mechanical hardness peaks at 2.0 mTorr due to twin and grain boundary synergy.•Precise pressure control yields dense Cu films with low stress and roughness.