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/Al
₂
O
₃
for ALD are being studied while ferroelectric thin films Au/Ti/BaTiO
₃
for sol-gel and Cu/Ba
_{1 - x}
Sr
_x
TiO
₃
for sputtering are being discussed in detail. The upper Au/Ti electrode layer is deposited by dc magnetron sputtering on top of Al
₂
O
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/BaTiO
₃
/Cu/SiO
₂
/Si (sputtering process). After a careful comparison is done, ALD for the Al
₂
O
₃
thin film seems to show the most promising process for its low temperature at 150 degC and for its electrical properties like a capacitance of 0.88nF/mm
²
with less then plusmn2% tolerances, a dissipation factor of less than 0.018, and a low leakage current less than 0.1 muA/cm
²
at 4V