Novel flexible and thin capacitors with Mn-doped SrTiO3 thin films on polyimide films

Novel SrTiO₃-based flexible and thin capacitors with total thickness of only 40 μm have been developed as decoupling capacitors. The sputter-deposited SrTiO₃ thin film capacitors, with electroplated Cu terminals, are fabricated on polyimide-coated Si substrates using photolithography and thin film process technologies. The capacitor parts, including polyimide, are finally peeled off from the Si substrates. Manganese impurity doping into the SrTiO₃ is effective for good uniformity and low temperature deposition down to 250°C. A highly elastic molybdenum film, as a part of the bottom electrodes, successfully suppresses the polyimide contraction during SrTiO₃ deposition up to 400°C. The diced flexible capacitor shows a large capacitance density of 3.2 nF/mm², and low leakage current of 10^-7 A/cm² at 10 V.