All-Solution Thin-film Capacitors and Their Deposition in Trench and Through-Via Structures

Thin integrated passive devices (IPDs) will play a critical role in the miniaturization of future high-performance electronic and bioelectronic systems. Silicon-based capacitors are currently manufactured with expensive processes such as sputtering and atomic layer deposition. Solution-deposited electrodes and dielectrics in trench and through-via structures provide alternative low-cost routes. Two solution-deposition techniques, spin-coating and vacuum infiltration, are investigated in this paper. A representative all-solution-derived thin-film capacitor consisting of sol-gel lanthanum nickel oxide (LNO) as the electrode, and sol-gel lead zirconate titanate as the dielectric thin-film is demonstrated in the first part of this paper. The role of barriers in reducing leakage currents is studied using three electrode systems: LNO/Si, LNO/ZrO₂/Si, and LNO/Pt/Ta/Si. Capacitors with LNO electrodes directly deposited on naturally oxidized silicon resulted in higher leakages, more defects and a lower yield. The results show that the zirconia barrier suppresses the leakage current in the dielectric. The second part of this paper describes sol-gel films deposited in the through-via and trench surfaces to demonstrate the sol-gel conformal coating technique. Scanning electron microscopy cross-section analysis shows that the vacuum infiltration conformally coated through-vias. These solution deposition techniques may have the potential to fabricate IPD capacitors at low cost.