Comparison Study from Sputtering, Sol-Gel, and ALD Processes Developing Embedded Thin Film Capacitors

Three methods for fabricating thin film capacitors are investigated using sputtering, sol-gel, and atomic layer deposition (ALD) techniques for advanced packaging applications for embedded capacitors. In particular, the microstructures and the electrical properties of ceramic oxide films Au/Ti/Al₂O₃ for ALD are being studied while ferroelectric thin films Au/Ti/BaTiO₃ for sol-gel and Cu/Ba_1-XSr_XTiO₃ for sputtering are being discussed in detail. The upper Au/Ti electrode layer is deposited by dc magnetron sputtering on top of Al₂O ₃ (ALD process) and on BT layer to complete the Au/Ti/BaTiO ₃/Ni/Cu/FR4/Cu (sol-gel process) structure respectively whereas Cu is deposited by sputtering on top of the BST layer to complete the Cu/Ba_1-XSr_XTiO₃/Cu/SiO₂/Si (sputtering process). After a careful comparison is done, ALD for the Al ₂O₃ thin film seems to show the most promising process for its low temperature at 150degC and for its electrical properties like a capacitance of 0.88nF/mm² with less then plusmn2% tolerances, a dissipation factor of less than 0.018, and a low leakage current less than 0.1muA/cm² at 4 V