FIB/SEM for inline 3D metrology and defect analysis

We investigated milling ion species interactions with materials and their influence on primary FIB/SEM applications used in the semiconductor manufacturing industry. SRIM simulations of 30keV Ga⁺, Xe⁺, and Ar⁺ at varying mill angles indicated Ar⁺ should produce reduced artifact cross sections and angled mills of dissimilar materials, with the lowest differential sputtering rate compared to Ga⁺ and Xe⁺. The SRIM-predicted interaction volume sizes and experimental evidence suggest that Ar⁺ also exhibits superior corner erosion, providing additional advantages for cross-sectioning applications. When milling normal to a silicon surface, the SRIM simulations indicate that Xe⁺ is the optimal ion species for deprocessing and other gas-assisted processes. The shallower penetration depth and increased concentration of energy-to-recoil events near the surface create more reactive secondary electrons and excited surface atoms near the surface of the silicon, which results in more uniform and planar deprocessing, and better gas assisted depositions. The milling performance for 30keV Ga⁺, Xe⁺, and Ar⁺ was investigated for common applications used in 3D FIB/SEM metrology. The results validate that the FIB source ion species can strongly influence the performance of different applications used in FIB/SEM metrology and defect analysis. Gallium (Ga⁺) ions are optimal for defect analysis through cross sections. Xenon (Xe⁺) ions perform best for planar deprocessing. The reduced differential sputtering between dissimilar materials and increased corner erosion enables Argon (Ar⁺) ions to produce high quality cross-sections & angled mills at significantly higher mill currents relative to Ga⁺ and Xe⁺, resulting in significant throughput enhancements.